Why do Swordmasters replenish just as fast as Spearmen? Why do I regain Stormvermin as fast as Skavenslaves?
One of the (many) reasons why elites replace all low tier troops in mid- to lategame is that low tier troops lose units faster than higher tier ones, but replenish just as slow (or fast), so going with the elites is more efficient and beneficial. This needs to change because it makes no sense. There's exactly one source of Swordmasters for HE and Stormvermin are way rarer than the more common Skaven, they should not be able to reinforce at the same speed. That's just two examples, but it applies on all factions, be it Greatswords, Chosen, Black Orks or Temple Guards.
So here's a suggestion: apply a modifier to the net replenishment rate (after every other bonus or malus has been applied) of T3-5 troops, something like x0.75 for T3 to x0.25 for T5. When your rares and elites are caught in an attritious battle, not being able to have them at full strength immediately afterwards should be something to consider, so a line of only Swordmasters would have an actual downside (I would go even further and just make replenishment bonuses through research, skills and items simply not apply to higher tiered troops at all).
Please consider it, @CA