The thing is that all Pokes are strong/weak only when compared to other Pokes. I understand that one move or so would take a number of underused Pokes and bring them to the competitive table, but this does a number of things.
Mostly, it further divides those particular ones with the others beneath them. If someone wants this one guy given one or two extra moves to bump up his usefulness, that only further makes Pokemon like Dunsparce utterly useless. In turn, people would start bickering that very underused Pokes like Dunsparce and Sunflora should now get a bump up. If this were to happen, the balance of the game would continue to shift, and people would start complaining that now the Ubers aren't as strong or powerful as they were intentionally meant to be, and that they should be bumped up. It'd be a process that never ended. We'd have Dunsparce with 2 evolutions and the like, which was never it's intentions. Not every Pokemon was designed to be playable in every situation.
I like the way Lofty suggest on the first page that instead of just making all underused Pokes more powerful, we should give them traits or moves that help them to become more useable in certain situations. Moves that he suggested, such as Rapid Spin are a perfect example. The move doesn't make Pokemon like Forretress extremely powerful, but it does open up his usefulness to the standard competitive game. I liked the idea of giving certain Pokemon moves that would enhance others, such as the Hive Call making Pokes with multi-hit attacks more useable. I think if they instead focused on making more of them more useful in certain situations this would make a lot of them more playable, without upsetting the balance of power within the game. Otherwise we could just sit here all day bickering about how this guy needs this super-powerful move and whatnot.