Agree, the enhancement request is a good way to get your voice heard.
Also, the limitation on 32-bit integers for double quantities translates to a limit of 16GB for the temporary storage (really, potentially larger than that, as I am only considering the non-zero values here, no other arrays such as indexing). 64-bit integers wouldn’t dramatically change the possible sizes, even on the largest of GPUs, currently.
On your 12GB titan, if the zero fill-in is hitting the ceiling, the ceiling it is hitting is your memory size, not the 32-bit integer limitation.
Since there are no provided examples in this thread, it is impossible to know if zero fill-in is actually the problem (or what the problem actually is), as that depends on matrix structure, which cannot be inferred from simple descriptions like dimensions or the number of non-zeros.