I have enabled Lua directory lookup based on the example at http://wiki.freeswitch.org/wiki/Lua_freeswitch_dbh#Lua_Script_2. It works ok, however I didn't figure out, how to properly group and isolate registered users to allow multihoming.

IMHO the best isolation is through different contexts. The context names are saved also in the DB together with the individual users. Hence the context dialplans cannot be specified on the file system as xml files. The dialplans are fairly static, they don't vary with each context.

Any idea how to make Freeswitch create those dialplans dynamically? 

Regards,