Implementing FMC (ANSI/VITA 57.1) in an Altera Device

[Altera_Forum]

I'm currently working on an FMC (ANSI/VITA 57.1) carrier board and have been running into a number of roadblocks implementing the FMC IO requirements in Altera devices. The FMC spec requires IO lines to support both single ended and differential while acting as either inputs or outputs.  

 To fully connect each FMC mezzanine requires 80 differential (160 SE) IO. Due to IO limitations on the projects main FPGA (Stratix IV GX), I was thinking of using a 3 smaller FPGA's (Cyclone?), one per FMC, as interfaces to the respective mezzanine and for some minimal front end processing. However, it seems impossible to implement the FMC spec using Altera parts without going to a high-end (expensive) Stratix series device.  The main issue is the differential IO can be either inputs or outputs depending on the application. The IO in Altera devices does not appear flexible enough to make this possible. To get around this, I considered using BLVDS with external resistors set up for a simple point to point configuration. This solves the differential input/output problem, but, makes using the lines in a SE application impossible. Even then, the split between emulated and true LVDS in most Altera parts and the shear number of differential IO required for a fully defined FMC makes it difficult to find a solution without going to a massive device. Other issues arise due to the lack of internal termination in some parts.  The solution seems so simple using a low end Xilinx part with SelectIO (Spartan 6), however, I'd prefer to use an Altera part for a variety of reasons. I searched the website and forum and almost nothing is returned for "FMC".  Has anyone implemented an FMC compliant interface using Altera devices? If so, what device did you use and were you able to maintain the flexibility of the FMC IO? Am I missing something or simply looking at the wrong parts? Cyclone V looks promising, but, is not available yet. Is it even possible to implement FMC with currently available (relatively inexpensive) Altera devices? Any help/advice would be greatly appreciated.  Thanks, Chris