Hi Roman,
Until now i used ClrMamePro mostly for MAME, but lately i started to play with other romset and emulators... MESS, Tosec, No-Intro, etc.
Working with different collections i think that could be useful a setting where it is possible to define a "read only" path where searching for rom, but NOT delete them regardless the flag 'remove matched sourcefiles' in the rebuilder windows.
This can be really handy if you want, for example, rebuild a set for a new version of HBMAME starting from an existing MAME ones you already have, plus dowloaded archives... or FinalBurn Alpha starting from a MAME + downloaded files, or a No-Intro from Tosec + download, etc. etc.
In this way while rebuilding you can clean your download/temp rom directory from multiple copies of the same file, but leave untouched the good sets you already have.
Hope to have explained mi idea, sorry but english is not my first language
PS. have a couple more of user defined setting for the compressor would be nice too... people can have different configuration for the same kind of archive, like 7zip with or withoud solid compression
Thanks
Davide