It's simple, really.
A shield meter.
I mean, currently, we can try to activate our shield to see how much more we can take but that gets to be a pain. It'd make life a lot easier if we could see a tiny little bar, gauge, circle, or something that showed what stage/color our shield was/is currently at.
That's all.
I'm against a actual bar, much for the same reason I dislike all the "weapons need numbers!" chat.
(not going into that, suffice to say I don't like there being a 'best' piece of armor or equipment)
I would like some sort of flash when your shield is full recharged tho.