Depends on what you mean by 'materialised'. The biggest Lib Dem lead, in percentage terms, was 3% over the Conservatives by YouGov on 19-20 April (Lib 34, Con 31, Lab 26). Seat wise, the Electoral Calculus projector gives Lab 238, Con 226, Lib 150, SNP 7, PC 4, Oth 3.
If we're assuming those seat numbers, then it would've been a Liberal Democrat choice of government. They may have been more inclined to discuss with Labour than they were in real life, due to them being the largest party and being able to form a stable government together (unlike the requiring support from the SNP+Plaid to get a bare working majority).
Gordon Brown was a major stumbling block to a Labour-Lib Dem deal in real life, he may have been more reluctant to resign had Labour been the largest party. I'd imagine, however, that a Labour-Lib Dem coalition would've emerged.
Is there a chance that Clegg could actually be in a good enough position to be made Prime Minister? I mean, he could pick whoever he wanted and switch over if he ever felt like it. That’s a pretty strong position to be in.
One thing I didn’t realize is just how equally spread the Lib Dem votes are - to get over the other two parties, they have to hit almost 40% and beat them by 10%+. No wonder they want the system reformed!