I also like a high-threat game, but I like ammo dice. Anyone who wants to stay alive will adapt to a high-threat environment will be by avoiding contact, especially if the enemy is better supplied.
If you rejig the ammo dice rule then you're changing the rules for all combatants. An enemy who is well supplied and unconcerned with ammunition is now operating under tweaked game rules designed to favor conserving ammo, when in the real world the winning factor in most small unit engagements will be volume of fire. And this brings up an assumption we see throughout this thread: that experienced troops use less ammunition, while inexperienced troops shoot wildly. This isn't so: experienced troops know that volume of fire wins, and they will dump fire onto the enemy while moving into position to finish the job the old fashioned way, with high explosives.
I can't tell you how to enjoy your game, but from the standpoint of making a sensible combat system, high ammo consumption wins fights.