I know I've tweaked the unit availabilities in my own copy of EB1 to allow access to "local elite" type units for anyone who now doesn't have model-sharing issues with them. It's not like kings and noblemen were particularly opposed to fighting for foreign masters if it suited them, after all. (OTOH high-end units that somehow involve some very "faction-specific" organisational infrastructures, reforms thereof or something similar I've left out.)