I think it would be cool to have a button where we could open our phantom cards so we could view what we got.

I also think it would be cool if we could save our ladder prizes for a week or more so we can have more phantoms at once.

I like the first idea, I dislike the second.
The ability to save up your reward would, I believe, only encourage ladder abuse again.As it is now, you can abuse and have at max 110 (I believe) ladder phantoms at once, what you are suggesting would make people want to abuse to save up however many phantoms they feel like and then be able to make the super deck for almost 3 weeks and win all of the ECs.
Maybe being able to save them but only being able to claim 55 (or whatever top place gets) a week? That could be useful if you are going on vacation for a week and dont want your phantoms rotting,want to save up your 10 a week you get and instead have 55 after a few weeks of work, or if you just have enough phantoms already and dont feel like working hard on the ladder for a while but still want to have phantoms when these expire.