1) True: there is no "blank all" command or equivalent.
2) Here are some rules of thumb for "cleaning" most modern Motorola subscribers:
A) Start by modifying all conventional personalities to set "scan" at "none." (Hint: the "Edit Field Down" function on Astro25 CPS is helpful here, but there is no equivalent command for Waris radios.)
B) Now you can delete all scan lists other than Scan List 1 without errors. Reset Scan List 1 to single entry of Z1C1.
C) At this point, you should be able to delete all zones other than Zone 1 without errors, and all channels in Zone 1 other than Channel 1 without errors.
D) Reset Zone 1 Channel 1 to a base frequency (450.025 in UHF radios), simplex, CSQ.
E) Now you should be able to delete all MDC systems (except 1) and the like, without errors.
F) Most people would stop there.