Let's discuss potential evolutions, pre-evolutions and mid-evolutions for single and two staged Pokémon lines according to their weight and height, p2

Potential pre-evolutions according to weight and height:

Lunatone, Solrock,Scyther,Torkoal,Cryogonal, Seviper, Furfrou, Zangoose, Hawlucha, Stantler

Potential pre-evolutions or mid-evolutions according to weight and height: 

Skorupi-Drapion: Skorupi goes from 0.8 m and 12.0 kg to 1.3 m and 61.5 kg. The line has 170 BST gap.

Skorupi's height and weight are comparable to a second stage so a pre-evo can work, but it would be difficult due to its low BST.

Due to massive BST gap, a mid-evo can work, especially with the weight increase, but since height increase is not that significant, it is a bit iffy.

Potential  mid-evolutions according to weight and height: 

Potential evolution or pre-evolutions according to weight and height:

Goldeen-Seaking: Goldeen goes from 0.6 m and 15.0 kg to 1.3 m and 39.0 kg. Goldeen has 320 BST, and relatively high height and weight, so an 250 BST pre-evolution can work.

More clearly, however, Seaking has 450 BST, which is perfect for an evolution.

Koffing-Weezing: Koffing goes from 0.6 m and 1.0 kg to 1.2 m and 9.5 kg. Koffing has 340 BST, and is fairly large, so a small pre-evo can work.

More clearly, however, Weezing can get a Magnezone-like evolution.

Slugma-Magcargo: Slugma goes from 0.7m and 35.0 kg to 0.8m and 55.0 kg. There are no significant changes upon evolution, even with the added Rock-typing.

The line has 160 BST gap, and Magcargo has 410 BST while Slugma has 250 BST. Magcargo's stats are ready for an evolution, especially considering its late Level 38 evolution.

While Slugma's stats are pathetically low, its height and weight aren't, so an early-game pre-evo that is just a small flame can work. It would need to have Sunkern-like stats, however.

Smeargle: It might not look like it, but it has 1.2 m and 58.0 kg. It is effectively a second stage fully evolved Pokémon.

While its BST is low, 250, with its gimmick, a pre-evolution can actually kind of work.

Volbeat, Illumise, Spinda, Relicanth, Carnivine, Maractus, Carbink

Mankey-Primeape: Mankey and Primeape have 0.5 m and 28.0 kg and 1.0 m and 32.0 kg respectively. Mankey's height and weight are comparable to a middle stage, but a pre-evo is tricky, due its low BST.

However, with its low BST, and low height and weight, Primeape is perfect candidate for an evolution.

Potential evolutions or mid-evolutions according to weight and height:

Spearow-Fearow: Spearow goes from 0.3 m and 2.0 kg to 1.2 m and 38.0 kg. The line gains significant amount of height and considerable weight. The line also has 180 BST gap, making a mid-evo very fitting.

However, Fearow also has low BST, 442, and evolves early, at Level 20, making it perfect for an evolution.

Krabby-Kingler: Krabby goes from 0.4 m and 6.5 kg to 1.3 m and 60.0 kg. The line gains significant height increase, and has 150 BST, making a mid-evo plausible.

But Kingler has low BST, 475, evolves early at Level 28, and has a version counterpart who has an evolution, Seadra, making an evolution more fitting.

Smoochum-Jynx: Smoochum goes from 0.4 m and 6.0 kg to 1.4m and 40.6 kg. While weight gain is not too big, height gain is. So a middle stage can work. But 150 BST gap and Level 30 evolution makes it a bit tricky

Jynx also has low weight and acceptable height, as well as 455 BST, making it perfect for a evolution.

Shroomish-Breloom: Shroomish goes from 0.4 m and 4.5 kg to 1.2 m and 39.2 kg. The line has 165 BST gap, and significant height gap, so a mid-evo can work.

Breloom also has low BST, 460, evolves as early as Level 23 and is fairly light, and small, so an evo can work, ignoring its gimmick.

Shellos-Gastrodon: Shellos goes from 0.3 m and 6.3 kg to 0.9 m and 29.9 kg. The line gains a significant amount of height, and has 150 BST gap, so a mid-evo can work.

But Gastrodon has 475 BST, and has low height and weight, so an evolution can also work.

Drifloon-Drifblim: Drifloon goes from 0.4 m and 1.2 kg to 1.2 m and 15.0 kg. It has 150 BST gap, and significant height gap, making a mid-evo plausible.

But Drifblim is also fairly small and very light, so an Electivire-like evo would be more fitting.

Phantump-Trevenant: Phantump goes from 0.4 m and 7.0 kg to 1.5 m and 71.0 kg. While the weight increase is acceptable, the height increase is significant. In addition, the line has 185 BST gap, so a mid-evo would be a good fit.

But, Trevenant also has low height and weight, so a Electivire-like evo can work.

Joltik-Galvantula:  0.1 m and 0.6 kg to 0.8 m and 14.3 kg. It evolves at Level 36 and has 153 BST gap, so a mid-evo is plausible.

However, considering Galvantula's comparatively small size and low weight, it would be more fitting to an evolution.

Voltorb-Electrode: Voltorb goes from 0.5 m and 10.4 kg to 1.2 m and 66.6 kg. Voltorb gains considerable height upon evolution, and the evolution line has 150 BST gap, so a mid-evo can work.

Similarly, Electrode has low BST, and is not too large or heavy, so it can get an Electivire-like evolution.

Spritzee-Aromatisse: Spritzee has 0.2 m and 0.5 kg and goes to 0.8m and 15.5 kg, gaining significant amount of height and weight. The line only has 121 BST gap, however, so a mid-evo can barely work.

While Spritzee has a high 341 BST, it is too small and light to have a pre-evo.

Similarly, its evolution, Aromatisse, is small and weak enough to justify an evo.

Potential evolutions, pre-evolutions or mid-evolutions according to weight and height:

Fossils: Most fossils have basic stages that are powerful and large enough to justify pre-evos, evos that are powerful enough to justify a mid-evo, and weak enough to justify an evo.

Binacle-Barbaracle: Binacle goes from 0.5 m and 31.0 kg to 1.3 m and 96.0 kg. The line has a massive 194 BST gap, and evolves very late at Level 39, making a mid-evo very fitting.

However, Binacle's weight and height are comparable to a middle-stage, so a single Binacle, possibly with 250 something BST, can work as a pre-evo.

Similarly, Barbaracle is not too heavy for a Rock-type, so a Scizor-like evolution can work to bypass its already high 500 BST.

Potential evolutions according to weight and height:

Persian, Heliolisk, Marowak, Swanna, Meowstic, Dedenne, Plusle, Emolga, Minun, Pachirisu, Swoobat, Sunflora, Sudowoodo, Liepard, Simisage, Simisear, Simipour, Swellow, Masquerain, Pelipper, Chimecho, Cherrim, Escavalier, Accelgor, Beheeyem, Slurpuff, Kricketune, Delcatty.

Lines where additions do not make sense much:

Nincada-Ninjask/Shedinja: 0.5 m and 5.5 kg to 0.8 m and 12.0 kg/1.2 kg. The line has 190 BST/-30 BST gap and evolves at Level 20.

While an evolution would be cool for both stages, it is biologically untenable. A cocoon stage also cannot work, because cicada nymphs do not work that.

Cottonee-Whimsicott: 0.3 m and 0.6 kg to 0.7 m and 6.6 kg. The line has 200 BST gap.

While the BST gap is significant, the line is specifically designed to not change much. So an addition cannot work.

It is also designed to be powerful but adorable, so an evolution cannot work either.

Petilil-Lilligant:  0.5 m and 6.6 kg to 1.1 m and 16.3 kg. The line has 200 BST gap.

While the BST gap is significant, the line is specifically designed to not change much. So an addition cannot work.

It is also designed to be powerful but adorable, so an evolution cannot work either.
Lines where additions do not make sense much but I want anyways:

Mismagius: Mismagius has 0.7 m and 1.0 kg. It is large enough to have a pre-evo, and has high BST to do so, but its evolution is not too strong, and it is very light. But I want a pre-evo regardless.

Murkrow: Murkrow has 0.5 m and 2.1 kg. It is large enough to have a pre-evo, and has high BST to do so, but its evolution is not too strong, and it is very light. But I want a pre-evo regardless.

Minccino: Minccino has 0.4 m and 5.8 kg. It is small and light, its evolution is not too strong. But I want a pre-evo regardless.