Business-wise, it makes sense to use 5 VAs. Pretty logical for any company, really. But (and this is trivial, I know) I feel it's a waste since they're identical quints they should have the same voices too. It's how they tricked the MC a few times after all, not just change their looks.
Oh well, like I said: trivial. Hope this gets a proper treatment and not the typical watered down and do-their-own-thing (especially the endings ><) anime. It's why I quit watching anime as a whole. (To give a timeframe, Negima! was the last anime I watched and other anime were treated the same as it. Got sick of it so I stopped.)