In real life many of these have a minimum distance afaik. Putting that aside:
Helis are not necessarily deployed against SAMs.
Bombs, ATGMs, anti-radiation missiles much more likely.
Artillery. The key word is artillery.
Honestly, they should open up some of the air map for GRBs but only for SPGs and SPAAs. It will add a bit of a Hide and Seek for CAS, but at least they will have their own mini-game.
SPAA would be relatively safe from most ground threats (IRL not all of these systems are deployed so close to an active front line).
SPGs new task would be: provide indirect fire support against ground targets on main-ground map, provide counterbattery fire, and finally: attempt to snipe SPAA. Yes with the addition of counterbattery radars.
Light tanks could fly their drones to actively scout enemy SPAA, or SPG. Would declutter main ground map which is also why the small maps are problematic. This is also why CAS jets are OP - they dont really need to look for ground targets. They would also feel more threatened, as SPAA could be in many other places.
SPAA and SPG gameplay would be more active/ engaging.
SPG wouldnt be OP because shell travel time, and terrain. With everything being equally threatened targets would move perhaps more often.
Helis could scout. Since there would be an opening somewhere, that they could exploit, they could fill the traditional flanking/ cavalry role.
Anyways on the side note: SPAAs at the moment they are already a waste - considering they can do only one thing really. There are ways to use Helis even within the current meta really. If SPAA sits back and they cant provide coverage to their team, their team would be exposed to attacks from CAS and Helis - most players from what Ive seen actively pick an SPAA if they get killed by airborne threats. Eventually the enemy team will be full of SPAA or weaker vehicles that ground forces can exploit. So i that way, Helicopters are enablers within the current meta.
Those of us who know the general flow of a match, will leave after the first death - cause this snowballing effect is very much real.
Top-tier is totally destroyed by map flow and gameplay flow. CAS, and how strong it is, is a symptom, rather than the cause.
Giving helis FnF weaponry- Im not sure it would solve any problems for Helis.
Going back to tactics - scout before moving in. RWR can be used to scout as well :) I normally tend to be aware of threats - doesnt mean I wont die to it. Im not an experienced heli-pilot within war thunder - but I try to be methodical.
What I try to avoid: cresting. Nothing is more visible than peeking over a hill - I do it at times for a quick view with the high zoom camera. Than I get back quick to make up a plan, estimate if enemy is aware or not. If aware, Ill try to sneak around. I use low altitude to protect myself. Rather than cresting over, I try to sneak up in a valley to get closer, and remove the threat with alternative approaches - rockets, guns or if the enemy is not aware a missile. Would Hellfire Limas help? Definetly. Do I consider them essential? No.