I would not wish to use such a thing if it meant that only the selected troops could be healed - that would, I think, leave the infirmaries empty when different level troops than those selected were injured.  But if troops already in the infirmaries could be replaced by troops of the selected type perhaps there would be a use for it.

That said I think the default case is that where there is space in the infirmaries the highest level troops have priority.  And that seems generally desirable.

That doesn't match my observations tbh. Mine fills up with lvl1 Scouts and so leaves all my lvl4 and up troops out in the cold. Makes it hard to get my monthlies for healing at times as there you need lvl7's minimum. Thats also why I mentioned it being optional. At times I DO want/need to heal those Scouts/lower lvl troops. 90% of the time though, I'm losing the chance to heal my 7's because its filled up 1's. Due to the speed I'm being hit by OS's in Jot (especially) being able to choose what levels to heal would be a major plus for me. 

If you follow the present vogue for using tier 1 troops for the meat shield I imagine it is the first OS which fills your infirmaries with T1s and the second OS which takes out the higher tier troops.

You might abandon the idea of a meat shield and rely on a peace treaty shield instead.  Offence has supplanted defence so the meat shield idea is somewhat old hat.

Well, I don't use a "traditional" meatshield anyway. Tired of healing 1's lol. I keep enough 1's for any possible amount of yielding. Thats it. Well, except for Scouts and I never use them myself. My main meatwall is 4's with a back-up of 6's. My 7's and eventual 8's (if I live long enough lol) are my sole fighters.

It was taking 2 or 3 OS's to deplete my former wall of 1's its just too much trouble to keep training/healing them. In the seconds it takes to choose them (to either x out or start the healing process) other Os's would hit and BOOM lots of dead 4's, 6's and 7's with no hope of healing because they never even had a chance to hit the infirmary. 

I understand my suggestion is NOT for everyone, why I suggested it being optional, but for some of us it would be a real boon. Me at least lol, so Plarium! , come on now make that change for the Dummy! ;D