I had never the feeling, that the standalone release of the games helped them very much in terms of activity.
Promotion is much more important in my opinion.
If you have a well-documented installation guide like we have here or in foreign-language commuties or even people around, that would help in any questions, it does not really matter if a release is a mod or a standalone.
The bigger problem in running freespace was not the installation of mods, that is quite easy in comparsion to many other and more successful games. For me it was always the unlimited number of options, you have in the launcher. Without any guide any new player does not have an idea what to select. It does not matter if you have a standalone or a mod. The problem is the same.
But i think that promotion in general is much more important, because i am not sure if most of you here here knows, that there is a complete Starlancer Standalone Total Conversion based upon Freespace's engine out there, even for dreamcast, for nearly two years, for example. But without any promotion, you will not get any new players here.
So, spread the word
. Create and updates forum threads in your gaming communites and in the GOG and Steam forums, where you can buy this games, regulary. Try to write Press releases. like every other publisher and developer do, even the team for Nehrim and a few others community teams did that, and send it to gaming websites to appear on them or write the news yourself, if your favorite magazine support that.
That is the thing that will really help.