I propose that instead of 4th tier QBs having flashing icons, maybe it could go like this:
First, a progression system would have to be added, so that players could set their QB's 1st, 2nd, 3rd, 4th and 5th reads pre-snap. Second, a progression rating would have to be added to simulate the QB's ability to read a defense. This would prevent teams from making LT their starting QB, because he has a high AWR rating. Even on his toss/pass option plays, he basically has 2 choices, run or throw to the deep guy.
5th tier (95+ PRG):
All icons available at all times.
4th tier (85-94 PRG):
4 icons available to start, 5th receiver comes in later on (1.5 seconds in). If there are 4 receivers on the play, 3 receivers are available right away, and the 4th comes in quickly (quicker than the 5th receiver on a 5 receiver play about 1 second in). If it's a 3 receiver play, all icons are displayed.
3rd tier (75-84 PRG):
3 icons available at the start, the 4th guy comes in later, and the 5th guy flashes. When there are 4 receivers on the play, the QB starts with 2 icons, the third comes in quickly, and the 4th flashes, but stays open longer. On 3 receiver plays, the first 2 receivers are open at the start, and the 3rd comes in quickly.
2nd tier (65-74 PRG):
2 guys available at the start, 3rd guy comes in later, 4th and 5th guy flash. The 4th would stay open longer than the 5th. On 4 receiver plays, the first guy would be open at the snap, the 2nd guy would come in quickly, and the 3rd and 4th would flash similarly to the 5 receiver plays. On 3 receiver plays, the first option is available at the snap, the 2nd comes in quickly and the 3rd flashes.
1st tier (0-64 PRG):
1 guy open at the snap on 5 receiver plays, 1 guy comes in, and the 3rd, 4th and 5th guys flash. The 5th guy is basically a decoy, since he'd be open for maybe half a second. The same principle as above would dictate 4 and 3 receiver plays.
This would simulate a QB's progression, while differentiating a QB's ability to read a defense and be aware of what's directly around him (aka the pass rush).