Rewarding teamwork is definitely a good thing. Strategus battles are way too much of a game of numbers.
Numbers should count however, so perhaps a tactic bonus similar to singleplayer, with amount of hirable soldiers should be enforced.
1000 vs 100, should be 100 vs 10 in the battle.
Still, with the respawn timer bonus. Say those 10 are armored knights and the rest mere light infantry, the Knights should have the advantage, and could perhaps push the KD ratio so far that they win in the end, or do far more damage to the enemy's number of troops.
Of course there are examples of players with 10:1 K:D ratio, but almost never for a whole team, unless they ran out of weapons or something like this. This is just a matter of experience and adjustment to find the right factors for the spawntimes.
Maybe make a server to test out the concept and adjust it in a "normal" battlemode?
Another note, please make it so that anyone can get accepted to a battle if no one has been hired 1 hour to 30 minutes before it starts.. Too many battles are playerless, and take up time in the Strategus calendar.. (Also all battles should have some kind of minimum equipment of simple spears and clubs, as well as some simple peasant armor for free by default)
Anyway, these changes could lead to people "Topping" their equipment lists, going for heavy gear in the beginning of the match to get a good initial K:D ratio, gradually changing it to cheaper gear. I think the consequences are interesting and should be tested!