Warband's battle mode consisted of a series of 1 life "rounds", at the conclusion of which everyone would respawn in starting positions and a new round would begin. Battle servers could assign custom gold amounts, which would be the baseline amount a player had every round. For instance, if I am given 1000 gold the first round, spend 976 gold out equipment, I have 26 gold remaining. The following round, assuming you died immediately and earned no gold, you will still default to 1000 gold, thus being able to buy the same baseline equipment you had the first round. Warband's system went further of course, and there was a whole formula about gold earned-gold spent on equipment for the next round (with different exceptions for looted gear/horses).
I'm assuming that for battle, the idea would be to have each player start with x amount (say 150), which ideally should enable every player to choose between the low-mid level classes for a single life. The following round, extra gold could be spent to afford the classes that are more expensive than x amount (say heavy cav at like 200). Therefore, in the first round you could choose to be a peasant, fight the entire round, and if you die, you have like 250 gold to spend on an elite unit. This was the basic principle that TW decided to morph into skirmish mode- essentially taking 2-3 concrete 'battle rounds', and turning them into a single 'skirmish round'. Unfortunately, I really see this system causing snowballing, cause a team that wins the first round with more than 2-3 people alive in a 6v6 will have a huge advantage in bringing elite troops to bear against the base classes the other team has.
A LOT of parameters would need to be adjusted, from team sizes to gold earned to class costs etc.