Hi,
it would be nice if during install the main Makefile would call the plugin Makefiles with install target.
Normaly this would be an empty target, but if the plugins needs additional files e.g. config files or sub-libraries they could be copied here.
Yes, I know that this change would break all plugins for the moment (until all have implemented an install target), so may be the main Makefile could grep the plugin Makefile for the install target and call it only when present.
I can prepare a patch if wanted.
Regards.