I don't think engineer should give vet, at least not t1, that way experimentals don't get unfair health bonus, I also like the
Regen idea where the unit gets a higher total life and an insane regen bonus for a minute or so , but this is currently dumb, also the rate at which the experimental gets its hp reward from vet could add to diversity (like maby monkey lord gets it really fast but the megalith has to wait 2minutes to get the full use of the vet). This only really needs to apply for experimentals, adding this to the acus takes out a fun aspect if the game, like when you have a hundred health left and kill the enemy acu, but in doing so get a vet that let's you survive the acu blast, these things at fun, it is not fun however when a monkey lord gets 2 vet entirely off the engineers assisting your air factory.