Players base isn't necessary the main reason modder mod.
BGF is its own mod so it is not compatible with FH2 and this is the reason why there is no problem of coexistence and that merging would rather be more harmful.(gameplay point of view incompatible etc ...).
If you see BGF or xww2 harmful to FH2 in terms of ressources, you had to look at the tournaments too.
About the limited ressources, sure, it is always a hard point, but animators etc can always be shared or ontract passed.
So good luck to them ! And i hope we will see finally all the works done after their first release