what about when what you want to disallow isn't weird or out there?!?!?
lets try this hypothetical
DM designs a basic 3.5 D&D world... says "Hey lets play, here is the world"
Player A says... "Cool, I want to play a half drow Warlock... my mom was a bar maid and my father a raider, I don't know where my powers come from, but I suspect my dad sold his soul to loth or something."
DM "No too weird..."
Player B says "I want to play a human Druid"
DM "OK"
Player A then says "OK, I'll play a Sword sage who travel's the world looking for new fighting styles"
DM "No, book of 9 swords is way broken"
Player B "My third level feat is the one that lets me cast in wild shape"
DM "OK"
Player A "BUT Sword sage is over powered?!?!"
DM "Just play something normal"
Player C "I want to be an Elven Ranger"
DM "OK"
Player A again "Fine, I'll play a sorcerer/monk with vow of poverty"
DM "No, I don't like that either"
Player A "So what can I play?"
I don't like these intentional corner case scenarios because they prove nothing in the end. DM's fully have the right to disallow whatever they want, even core. Now on that same token, you have the right ro refuse to play in his/her game. The reasons don't uave to be valid and the DM has always had the backup of the DMG. It's up to you to find a DM that fits your needs, what you don't have the right to do is enforce your wants on someone else unless they are willing to accept those. If the DM won't budge because he feels it won't fit or he just doesn't want that in his game then either play something else or find another game.
These scenarios are few and far between so they shouldn't be considered when making the judgement about book limits.