multiple live inferiors

Currently GDB supports having multiple non-live inferiors.  But, if I try to
add a second live inferior it wants to kill the current live inferior.

That is, I can do:

    gdb some-file.elf
    set non-stop on
    set target-async on
    target extended-remote | program with some arguments
    add-inferior -exec new-file.elf
    info inferiors
    inferior 2
    target extended-remote | program with different arguments

at which point GDB will say:

    A program is being debugged already.  Kill it? (y or n)

I'd be okay with the question if the current inferior was live.  But, it is just an executable.

I assume that there's more to changing this than just modifying target_preopen.
What else is likely to break or need modification?

Thanks.