This gave me an intresting idea... what about Technitian+Hidden Power? It would give CAP10 access to a BP 90 move of any type, but it only gets one. Now it could still recieve stuff like Ice Beam and T-bolt to make sure it can fill its movepool well, and also give it options incase you want to use a secondary ability, like Trace or Water Absorb or whatever. And don't say that Stratagem already can do the special Technitian thing-can it switch in on Salamence, T-Tar, or even Heatran consistantly?
It would still keep the customability of a Multitype pokemon, where it could be specified to beat certain pokemon, but it doesn't lock it into a single typing like Steel or Water. It also prevents the "counter everyting with one set" mentality if we give it every single possible 90 BP coverage move. It gets one good powered move of ANY type, plus what ever else we decide to give it. CAP10 could also use things like Icy Wind, which the speed drop from could shut down stuff like Latias.
Why not just go with Judgement then? It's a BP 100 move of any type (essentially) and it skips the whole need to play with IVs. Weather Ball also can be nice except the Pokemon who usually summon weather wouldn't be weak to the Weather Ball type. Still an idea. Also, we can always make a new move that always gets STAB or something. Heck, there's even the Doom Desire exclusive ???? typing which hits everything neutrally by itself.