1..Smoke repair is doctrinal but heavy sappers are not. Still having super repairs and such tanks in one commander makes it OP. Chrchill will deal dmg to crew weapons, tanks etc. and will come back fighting before those units have a chance to replace lost squad members or repair their own tanks. Churchill will start dealing dmg again with max health too quickly pushing axis off WP too easly. You just can't kite it forever.
2. I already explained what should be done imo (4 options): these repairs should be much more expensive, or panther should get tungsten rounds (similar to jacksons), or give ost/okw a satchel charge (could be panzergrens with shrecks or okw panzershreck sturmpios to prevent crushing them and punish parking it in the middle of at units), or make it simply more expensive to reflect its actual performance.
From my experience with the chill, when it damaged, it will have to fall back, the tank is rather slow and if snared, it will take about an haft of hour to get to some place where i can safely repair it without risking my engi taking arty, weffer or stuka. Then,after all the repair, it will take another haft of hour to drive the tank up to the line again. Somke repairs turn tank into a sitting duck ao pop it up in the front line is not a good idea.
Meanwhile Heavy sapper still repair slower than sweeper stumpio, plus OKW have a stock auto repair building.
Heavy sapper is a 60 amo upgrade lockes behind latest teck, while stumpio come out with support package from the stat.
My point is, the churchill doesn't come back to action supper quick as you clame.