Honestly Kage, I still see little problem in it.
First off, if someone were to ever have that many biju, then there is an issue in itself. However, he/she worked for it, so why do we want to restrict what they could do? It's one of those things where people wants to limit those who put in the work to get where they got. What's the point? They beat the odds, so let em play with the toy they earned.
One person with half the nine tails' power could counter all five of those Biju dama. So Kurama firing a biju bomb at one is essentially the same destruction.(and before we go into, "Well Kurama's bomb only knocked it off course" Just know that his bomb still caused the combined bombs to stop. If it was really so underpowered, the combined bijuu bomb would have torn through Kurama's like nothing.) What will we do then? Void Kurama or underpower him? At this point, I severely doubt that'll be the case.
All in all, I personally don't feel that one should have to give away biju that they fought for just because they're a Jinchuuriki of the x tails, and want to summon on the side. It limits RP for a jinchuuriki, defeats the purpose of fighting for em if you are one, and really is nonsensical. If you got the power fairly, why not use the power? Not to mention, what if you're by yourself? What does that jinchuuriki do in that situation when a spare biju falls in their lap? Can't summon it, so they're forced to simply drop it? Where? It's just too limiting.
That's all i'm really sayin, before I end up going in circles XD