Think of suppression this way:
First of all, usually the shooter is trying to hit a target if he sees it, even if the chance to do so is extremely low. (This is usually the case, if you deliberately shoot to miss and want suppression only, then just roll the ammo dice.) The lower your chance to hit is, the more likely you are to achive only suppression and no damage with ammo dice.
Now judge the results after the roll: If the shooter missed his base die but unloaded with lots of ammo then the shooter made the decision in the 5-10 sec time window to just suppress the target because the opportunity to achieve a good hit wasn't there. Or maybe he was actually trying to hit with full auto but the recoil made him miss, since like you mentioned, full auto is mostly used for suppression.
If on the other hand he managed to hit the target and spent lots of ammo it wasn't necessarily a full-auto barrage: it was short controlled bursts where only the last shots actually hit and had effect.
I've found out that a good way to run TW combat rounds when ammo dice are used is to actually describe afterwards with more detail what the character was doing, based on what the player was trying to achieve and the die results. Even in real life firefights seldom people go "Ok, I am gonna shoot that guy 4 times and then 3 times the other one", they fire until they reach the desired outcome on target or the opportunity passes. Controlled single shots being of course an exception (meaning no ammo dice, no recoil to affect the other shots).
This also allows you as a GM to highlight the competency of different characters: a librarian who just got handed his AK and misses you could easily describe as how the recoil surprises him and the last of the magazine is emptied towards the sky. A skilled spec ops guy who misses with the same AK probably missed his opportunity to hit with short accurate bursts but unfortunately the target was able to take cover etc.
Those are good ideas, and are inline with my usual GMing style. The issue I see is that this narrative approach is counter to the simulationist nature of T2k. Even though 4th edition is a much simplified version of the game, it's clear FLP has tried to keep its simulationist roots in place, and when we play this game, my players and I enjoy delving into the more nuanced aspects of combat, which lead to interesting tactical decisions.
For example, you only benefit from a stable platform with telescopic sights at the moment, so naturally players won't spend precious actions to slow aim unless they are using them. Some kind of recoil rule that would be countered with a stable platform would offer players more interesting decisions to make in combat, which after-the-fact narrative descriptions don't provide.