Mega Starmie leaning into physical Atk is just such a weird decision, it almost makes me think GameFreak was too scared they would break it if they emphasized Sp.A and Spe increases. But as it stands, its level up and TM compatibility in Gen 8 was almost exclusively special moves, with mostly just STAB and Normal as coverage among them (plus Gyro Ball lol). They're going to have to expand its movepool greatly, otherwise the Atk increase is entirely wasted. At the very least, I can see Fighting moves introduced into its pool just from it having long legs as a Mega.
I am happy to see Mega Meganium having a respectable Sp.A stat backed by good bulk. I'm sure it will have Dazzling Gleam, and hopefully Moonblast too since it doesn't appear there will be any new signature moves for the starters. All it needs is Earth Power and it should be at least decent, but I'm also crossing my fingers for Calm Mind. If it doesn't get Earth Power, I guess Body Press is there.
Hopefully the new TM compatibility list will come soon!