Since this is just a change to the ROM code, and the ROM space is the same as DK, is there any reason why it WOULDN'T work by just rewriting your ROM chips? You didn't have to do any MAME tricks or modify the dkong driver.
The only potential issue I could see is an actual, physical Z80 having to do these computations, as opposed to an emulated Z80. But the CPU clock and instruction set are emulated accurately are they not? It seems that if this new code was gonna cause buggy behavior, then those problems would show themselves in emulation.