My biggest grief would have to be wanting to play with cards to speed up a game and having the cards awarded completely control the game. If you're playing triples and your team gets red and green sets while the other gets mixed sets then the games is pretty much completely over for your team. This tends to ruin a game for me wether I win or lose.
In esc games people tend to skip their first turn or skip their turn if they're holding 5 cards and nobody has cashed in. This can really slow a game down in an otherwise face paced game.
What I would suggest would be another option for cashing in cards. Something where the cash in is added to each time the individual cashes in a set of cards instead of it being dependant on everyone in the game.
option #1:
1rst cash in = 4 (amount is negotiable

2nd cash in = 6
3rd cash in = 8
4rth cash in = 10
5th cash in = 15
6th cash in = 20
7th cash in = 30
so if player 1 cashes in once he will get 4 armies along with everyone else who has cashed in. The second time a person cashes in they'll get 6 cards. So if player 1 cashes two set of cards in he will get a total of 10 cards and if player 2 cashes in his first set after player 1 he will only recieve 4 cards.
or for escilating games that are dependant on everybodies cash ins
option#2:
1rst =4
2nd =5
3rd =6
4rth =7
5th =8
6th =9
7th =10
8th = 12
9th = 14
10th = 16
11th = 18
12th = 20
Then have it keep going up by 5 so the early stages of the game aren't decided by which order you cash in but instead mostly just there to help speed up the game.