You can do that, but it's slow as damn on an already slow as damn cpu. Qemu.
Existing example - darwine. Qemu + wine on a PPC mac could run x86 windows apps.
Anyway, as mentioned before, the problem with ARM is huge fragmentation. There still isn't a single bootloader or a single kernel that can boot on all ARM, there isn't a single graphics standard or an open-source gfx driver, and even the cpus vary enough to cause huge performance penalties via targeting. If you want to run on more cpus, you'll be over 50% slower on the latest ARMs (meaningless number, just as an example of the magnitude we're talking about).