There is no universe where Steven doesn't get a Mega Metagross let's be real here. While cool factor may have applied, his iconic ace has always been Metagross
I also doubt Mega Salamence was designed with Drake in mind at all, incidentally. Altaria doesnt even enter the equation, it's just the fact that the e4 rematches were very likely a late in development thing, their mega items are generic and not on their artwork, and likely would have been paired with their proper aces across the board (Dusknoir for Phoebe, Walrein for Glacia)
Salamence was probably made for Zinnia, who as a dragon trainer would make sense to have hoenn's most iconic dragon type (well, non legendary) and oh hey sure enough she's got the fancy mega item and Salamence as her ace.
I also doubt Mega Salamence was designed with Drake in mind at all, incidentally. Altaria doesnt even enter the equation, it's just the fact that the e4 rematches were very likely a late in development thing, their mega items are generic and not on their artwork, and likely would have been paired with their proper aces across the board (Dusknoir for Phoebe, Walrein for Glacia)
Salamence was probably made for Zinnia, who as a dragon trainer would make sense to have hoenn's most iconic dragon type (well, non legendary) and oh hey sure enough she's got the fancy mega item and Salamence as her ace.