I'm some-what on the fence about this suggestion...
On the one hand, I think it makes sense to be required to sacrifice something in order to hold wards, giving your team a tactical advantage in map awareness, while sacrificing a portion of your late-game potential... It's balanced how it is...
However, I also like the idea of a pouch... Maybe just an item, which still requires a slot, but has a small base stat on it such as a few Armour, MR or a small amount of health...
(Maybe 3 different options)
Having GP/10 on this item wouldn't get my support... Maybe if it was a very reduced number, not like Philo or HoG, but maybe 1/4 of their effect, meaning you'll never get back what you paid for it, but the cost of the item won't be quite such a huge strain...
You'd still be making sacrifices in order to ward, but it will be slightly less harsh if we had pouches, which still used up item slots...
Basically, I want supports to get a 6th item which gives 5-10 Armour or MR, and allows them to keep warding, which is quite a lot of programming for such a small stat increase, which is probably why it won't be implimented... But anyway, that's my 2 cents...
Diversity is never a bad thing...