you could still have off-map artillery in wargame, sure cruise missiles (as well as scuds and the like) is also an option but division and corp level heavy artillery was still a thing during the cold war.
Same with towed artillery, still very much a thing. You could even have ATGMs and recoilless rifles as specific dismounted non-infantry units.
Map maker, scenario maker and more objective-based matches would also be high on the priority list.
I agree that the phase system is a pretty good idea in theory. It needs a specific balancing but it does represent how large formations enter the battlefield and deploys from column formation. See pic, literally made for a phase mechanic