How about integrating the cheatmode as a switch instead of creating a second version for a few bytes changed? Entering highscore table should be skipped when cheat is enabled.
Another option would be to create a subroutine where during decrunch holding a certain key down to trigger infinite lives at the very start in onetime.asm For example
//Detect cheat key press (CONTROL)
lda $dc00
lsr
lsr
lsr
bcs nocheat
//enter code for giving player infinite lives
nocheat: do rest of onetime code