The problem is we can not all agree that "Sappers are fine-ish combat troops" since katitof claims they:
"are very bad in actual combat"
I suggest you test vet 3 heavy sappers vs any infatry you see fit in cheat mod and see how they perform.
They do pretty much what you would expect IMO. Dueling green cover at like 10 range 5 Man Sappers lose to Vet 5 Volks and Vet 3 LMG Grens but are fairly competitive. Anything else is what you would expect - they do better at point blank and worse farther away. Adding more Brens tips the scale in their favor. I guess it's up to you whether or not you think Anvil Tech + Heavy Sapper upgrade cost should let them be competitive against mainline infantry. If you're dumping more munitions into them and tying up your engineer/snaring squad in combat its more than fair I think. Any other situation it's just them firing the Vickers for extra chip damage at long range which is nonconsequential.