i like the idea of MD-esque TM restoration, and the mechanic could be introduced before the post-game for the weaker TMs since it would have to be tied to some form of resource (items, money, BP, etc). as i posted before i am a big advocate of weaker moves being early TMs (once again i say shock wave is the ideal example in basically any game it shows up) and they could be available for this mechanic before the post-game. i guess it wouldn't be much different from the TM machine of SV, but.. better.
speaking of shock wave, a movepool oddity eith the original eeveelutions: you obtain the celadon mansion eevee at level 25. in RB that's fine because the evolutions' STAB is learned later. however, in Y it was moved to a level earlier than 25, presumably because of the rival, but this means the evolutions go STAB-less for a while without TMs. thankfully, misty and surge give out bubblebeam and thunderbolt, so vaporeon and jolteon can evolve and be good immediately anyway. flareon, though? the only fire TM is fire blast, won after the usually 7th gym. it does have 130 atk for normal attacks, but that's clearly a worse trade-off.
come gen 3, and things actually carried on from Y in every way for FRLG - initial STAB locked behind the level you actually obtain the eevee, vaporeon and jolteon saved by the misty/surge TMs, flareon has to make do with normal attacks or you spend 80k to give it flamethrower.
this issue is less relevant in platinum because of the blizzard/thunder/fire blast TMs being purchaseable basically right after you get the eevee, and finally flareon did get the last laugh in B2W2/XY, with fire fang showing up in only a few level ups, while jolteon has to make do with thunder fang and volt switch for a while and, as some sort of sick joke, vaporeon has water pulse in its level up moves right Before the level of a wild eevee (in both generations!!), and then nothing but aurora beam until surf.
and then after only 7 generations they finally realised that hey, some mons need to learn moves right when they evolve. it only took them 20 years!