Well, that was simple. Just in case anyone else can't find the answer, I'll post it here. If you go into the server source, specifically ruletypes.h within the common subdirectory, you'll find a bunch of default settings. If you change the following line:
Code:
RULE_BOOL(World, UseClientBasedExpansionSettings, true)
If you change "true" to "false" and re-compile the server, the Titanium client will obey the server settings for expansions owned. I don't believe custom race/class combos would work, but it will at least force the client to obey Froglok settings if using an expansion limit prior to LoY and Berserker settings if the expansion is set before GoD.
Edit: I'm not sure, but I'd assume this variable could also be set in the rule_values table under the rule_name of "World:UseClientBasedExpansionSettings".