I wouldn't mind the rematch teams to be something like (assuming the remakes happen in Gen V, of course):
Sidney: Shiftry, Crawdaunt, Scrafty, Absol and Hydreigon. (He has a Sharpedo in his RS team but Crawdaunt in his Emerald; as Grimsley has one, I doubt they'd want to give Sidney one. Scrafty's there for type coverage though).
Phoebe: Gengar, Banette, Dusknoir, Sableye and Rotom (It would be cool if, in the Ruby remake, her Rotom is Wash Rotom, but in the Sapphire remake, it's Heat Rotom).
Glacia: Glalie, Cryogonal (why not? xD), Abomasnow, Froslass, Walrein.
Drake: Dragonite, Flygon, Garchomp, Kingdra, Salamence.
Steven: Skarmory, Bastiodon, Magnezone, Ferrothorn, Metagross.
Bastiodon fits Steven so well; as in RS he uses Almaldo and Cradily, obviously referencing his excavation-going-ness; Bastiodon is a fossil Pokémon - but is steel-type!