How to specify memory initialization files for multiple instances of one Nios design?

I want different applications running on multiple instances of a common Nios design. How do I specify unique memory initialization files? Put another way, how do I specify a memory initialization file outside of Qsys?

(I rather not have two Nios designs and two BSPs, different in name only.)

// for example:

// two instances of "nios_cpu..."

nios_cpu cpu0 (...); // this one should use cpu0_mem_init.hex

nios_cpu cpu1 (...); // this one should use cpu1_mem_init.hex

Thanks!

(This question was formerly posted as "Unique Memory Initialization Files for Multiple Nios Instances" but no useful replies were received.)