I have thought about it too... After first only evolving wonders and then just evolving level 30 even if they are not wonder, for at the end ending up with a bunch of pokemons i would never use. To strong for prestige, too week for fighting(at least compared with my elite team)
Honestly, I think it is something wrong with the game when we need to keep lots of varieties of the same pokemon in order to play efficiently. Why should we need 5 different levels of a Vaporeon...?
Yes, it would definitely be handy with a table as described. However, hopefully the announced gym rework would change the need of one...