AdiIRC

Not sure i like this idea, setting custom filenames like this will make it complicated to restore a log into a channel window. Even more with 2 different sets of filenames.

Any ideas to simplify it a little?

I would say, either (1)you use a kind of factory or (2)you enable just few passibilities.
To 1: factory use the current option for loading and saving of messages. If you change the option, then you disclaim the possibility to load messages with old saveing format.
to 2: you should save the current/last logging file for each channel in a configutation file(I guess .ini file) and then load from this file

I guess there are more possibielies to handle it.