there aren’t more enemies later in the game that are suitable for “farming” experience for raw recruits …
That’s precisely the problem, later on the game world gets harder and the company has no option of picking fights with weaker opponents, they all get stronger and/or more numerous!
Even if the new recruits could do some damage there is still the problem with AI focusing on the weakest unit whenever possible, so you have little choice but to make them an immobile tin can stuck in the back line. I say: boring!
Another option would be to simply give ALL the recruits some levels as the game progresses. Easier to do for sure, would make little sense fluff-wise but at this point I’d gladly take any solution other than the current grind.