I am unsure if this is already available, but putting it out there. 

The ability for a host to lock a seat for (a) certain player(s) in their game, but still have the ability over-invite for the rest of the positions.

Example. Cumber starts an 8 player dev game and wants to guarantee Nygma and Yertle a seat, and invites 10 other people to fill the remaining seats.

I would like this feature too.  I would additionally like to be able to invite ALL players in the over-invite category.

Obviously, we're talking about reserved seating, in which case the game can/should not be ranked.

By previous consensus, these would have to be private only, but I like the idea, especially for the purpose of trying to get new recruits hooked to the site.

What if you save a secured seat for Yertle and he declines the game?

That seat should be made available to all other invitees.  If no one has joined the game then I suppose the creator can terminate it.

I've added this to the Feature request list.