First, here are some thoughts I've had on the subject, in no particular order:
I would see the most obvious way to advance in Defiance would be to improve in the troop quality. Quality isn't arranged in clear tiers of course, since it's not immediately obvious where Fanatics should go and Matrix is something of an outsider in the entire scheme. Still I think a "decision tree" of some sort could be constructed to allow Quality advancement.
At army level, the force could start with a "cripled SR" (say with only 25% Elites allowed instead of the maximum bought) and then rise to the full potential later.
Becoming a hero/leader/commander outright might also work on a per-model basis, although it may be more difficult to determine how these should come a trooper's way.
Hand-outs, in other words augmentations and better (ie. costlier) weapons are another angle that would likely work to distinguish more experienced troops from the raw recruits. Stat changes in regards to armor and movement are a bit problematic because they might lead to a frame that doesn't normally exist.
A question that needs to be solved is how a unit that has advanced should be dealt with pointswise. Perhaps the most "fair" option would be to recost the troops as they advance, but that may get a bit tedious. Another way would be to make the campaign into something that must be committed to, as in Necromunda. New troops can be brought in but they aren't quaranteed to be able to go toe to toe (PVcostwise) with the more experienced troops, and the final balance would be accomplished by the most impartial of referees: chance.
Demian Rose wrote:I was thinking of a two-tiered system, whereby indidividuals gain experience, but the army as a whole also does, in some proportion to how many experienced members it's amassed; any ideas about how to do this easily?
As a partial tentative answer to this one, Wh40k at one point had a simple campaign system which didn't necessarily work very well, but perhaps could be elaborated upon. As far as I recall, a unit amassed experience for gaining victory points and lost experince for loosing them ie. through losses. So a base for an experience gain system might be to keep tabs on how many VP each unit gains from kills and scenarios (for being a "scoring unit", basically) and those VP could be used to buy advances and to replace losses. The problem in the system rises from the fact that in many games, units that do score VPs basically get wiped out in the process so they would have to use a large part of the VPs they garner simply to recuperate, not to advance.
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