Experience bonus/multiplier Question

Why do units that face battle not get an experience multiplier? It would make damaged units and the delay in repairing/healing them more valuable.

i.e, imagine a battle... 1 infantry A vs 1 infantry B. Infantry A wins. Now it does 1.2 damage on its base stats. it goes off to heal, etc. comes back 2 Infantry A vs. 2 infantry B... Infantry A would Always win (not subject to probability roll) because of the experience.

Also, units should be able to disengage from battle for a % penalty. but if they do... they get a negative experience multiplier.

Right now, the damaged units have no value even for later... they are not effective. only "research" provides an increase in effectiveness. Which should'nt be true.

i.e. researching tanks is obviously correct. but there is no difference between 1941 infantry and 1946 infantry other than the experience gained... it is why experienced units often win battles they shouldn't.

Perhaps a "training" bonus instead? Like an upgrade... but not quite?