Actually I've been using 1.3 and 2.04 on A500 and later 2.04, 3.0 & 3.1 on A3000 on a single partition. You just have to query the exec.library version in the beginning of startup-sequence to find out which ROM is active and assign C:, LIBS: etc. to the appropriate subdirs. Of course this doesn't have to depend on the ROM present but can also be used with ENVARC variables, so could just shell command
setenv envarc:OS 3.0
;-)
