I'm not sure it's possible. The whole thing is kinda dependent on avast! drivers... so, it would either be really standalone (meaning it would install the drivers itself, but avast! could not be installed on the computer in that case), or it would use the drivers of an already installed avast! - in which case, however, it would have to start updating with avast! (so that the drivers of the program and the application don't get desynced), which basically means turning avast! into Pro and let it update the thing itself.
Or, introducing a 4th avast! edition ("Semi Pro") - which would be Free + SafeZone... bringing a lot of confusion into the possible licenses, upgrades between them, ...
Just my opinion, but I'd say it's definitely not worth it - a lot of possible problems with questionable benefit.