I don't think a modern setting fits CoH - too many high tech high range weapon systems (like ATGMs) and focus on merging combat roles like the Main Battle Tank or stuffing all sorts of heavy weapons on recon/infantry fighting vehicles (like Bradley or BMP). Or all infantry having standardized assault rifle + LMG loadouts.
Something early Cold War (the end of the 'mechanical' warfare era) would be pretty interesting though. Basically 1950s-1960s with Pattons and T-54s and with light tanks like the M41 still in service could basically be a reskinned CoH/CoH2. The same mechanics and core but in a new and unique setting.
That's my concern with a modern setting, especially with infantry combat. How would one make any tactical decisions on how to engage other infantry units when they both have almost exclusively assault rifles and maybe SAWs? It'd also be harder to come up with a lot of varied infantry types since a lot of them use pretty much the same weapons now lol.