Looting enemies is the good practice, but you can't rely on it 100% because their stuff may be too high-tech to use yet.
What you're suggesting is basically that every mission in the game should be winnable no matter how ill-prepared you are.
I doubt it would have this effect. You may bring an unlimited amount of low-caliber bullets in the Bonny, but it will take an absurdly high amount of successful hits to kill a tank.
I computed the following stats for head-on shots to a tank, assuming 100% vulnerability, default HP and armors get chipped up to 1/3 of their normal value.
Your weapon power 75: 14hits (same as today)
Your weapon power 65: 20hits (same as today)
Your weapon power 60: 24 hits (instead of 25)
Your weapon power 55: 30 hits <- heavy machine gun
Your weapon power 45: 45 hits
Your weapon power 35 : 63 hits <- assault rifle/PS
Your weapon power 25 : 93 hits
Your weapon power 22 : 124 hits <- buckshot, old pistol
I won't bear people with many scenarii, but for example to kill a Provost with AK47 only, you'd still need to hit him 42 times in the back.
And what was that point on wasting HE?
Oh, I just now understood your answer : I meant wasting your last HE pack earlier on enemies which could be handled differently, and you regret it later when you find a though guy.