ASL can be extended to deal with modern weapon systems and vehicles.
I'm in complete agreement that it's just a case of the relative numbers you want to have in play. If you can get reasonable data for armor thickness/composition and armor penetration capabilities, working out odds isn't all that hard.
I've suggested before that helicopters should behave like trucks, spending movement points as a truck, restricted from hex entry as a truck etc. With the understanding that they can climb levels and get to "above terrain" where they could go full throttle and behave as if they were on a road. Balancing the MP values would be the trick, while allowing cautious movement close to the ground, and fast movement when there is less risk from running into things. Give them damage points like other aircraft (or LC), and add some rules allowing a TC to simulate autorotation in the event the damage points are lost.
SAMs can be modeled as SW/Guns, or as a variant to OBA type activity. The tactical combatants (i.e. on the board) might have a SAM umbrella from off board, as well as a ZSU or other gun-track and/or man-pack/vehicle SAM tubes on the map. Classify as light or heavy AA, and run with the original rules for those effects. Fast moving targets might get designated as small targets, instead of adding new rules. The effect is still that they are harder to hit, just for different reasons.
WGM can be modeled in ASL scale as any other SW/Gun/Vehicle-armament. With the two minute time frame, most missiles will have run their course during a turn. (TOW Wikipedia article says 20 seconds to reach max range.) If you wanted some reaction possible, then fire in prep, followed by the terminal phase at the end of advancing fire (with the shooter stationary and surviving d-fire of course). Defender fired WGM might shoot in d-fire (MPh/DFPh) and resolve after all Attacker WGM have resolved at the end of AFPh. Gives both sides a chance to deal with the incoming missiles before they hit. As opposed to "hah hah, I blew up your tank from 30 hexes away with a TH=8, and there's nothing you can do about it!"
Or make them one shot resolve type affairs like current guns/LATW. Factor in the "response" to the WGM launch with a minimum of rules. Extra MP expended reduces the TH number (vehicle maneuvers to avoid missile), or based on range (more reaction time) the TH number goes down; or both...
Increased effectiveness in weapons might mean you need a "modern TK" chart, and "modern armor values", but think of all the third world countries still using tanks with WW2 era technologies. You might have to come up with a set of conversion factors, or just extend the numbers to reflect current lethality and protection. A modern sabot round will go in one side and out the other on most steel only WW2 tanks. (Worst part is that this needs a bunch of research time with various reference manuals, easier to stick to infantry only if possible.)
For squads, if the new paradigm really is "firepower", perhaps most standard first line squads get 6 FP instead of 4. True fire-breathing-lead-slinger type units (for whatever reason, say under-rifle GL) get 8 out of the box. If the nationalities tactical doctrine favors movement during a firefight, you get assault fire. With (semi-)automatic weapons becoming standard at the squad level, spraying fire may be a default for all modern units, or may be a nationality distinction based on training/doctrine.
If the lowest maneuver element is a fire team by doctrine, then you get self-deploy/recombine capability. (Which might also need adjustments to the Smoke being NA for HS rule... but maybe that's chrome.)
LAW/RPG can be an inherent SW like MOL/PF, or take counter form if necessary. AGL should be SW/MA class items, with HE/(HEAT?) and possibly AP/SMOKE type munitions available to them. Deciding on ROF and ammo would be the sticking points. (Again more research.)
Want to model SMOKE from GL inherent to the squad, then that class/nationality doesn't pay the extra MF to place Smoke Adjacent. (But this is seeming like a chrome rule to me.)
Etc. etc. etc.
Design for effect!