"Which flavor of 8051 do U [sic] think will be the best for this?"

Sounds like a job for a Triscend E5; you can easily implement 4 UARTs and your I2CHIP interface in the configurable logic, and FastChip has character LCD support (logic & software drivers).
You might also be able to dispense with one of those Alteras (you don't say what size or what you're doing with 'em)