I'm going to try to not be offensive about this:
Free_Lancer, I know you make a lot of these suggestions hoping to improve things, but you have just joined this server. I assume, since it is suggested in how you talk about the game, you have played RO for a while. You must understand that, while cool, most of these ideas are not probably. I'll highlight a few things that make this particular suggestion improbable...
Eventually - The GM team, and Pandora in particular, are working very hard to do many things to make this server fun and fair and great, looking forward to a time when all the castles have been opened (LONG time away, IMO) and there are still more guilds who would actively use this feature is not something they have time to do.
for fun non WoE guilds - These types of guilds already exist, and exist on many servers (including the official ones). I, being a leader of one such guild, see no reason to ask the GMs to design an entirely new map (which is a lot of effort if map design in Ragnarok is anything like any other game I've worked on) just to cater to these guilds seems mildly ridiculous. No offense, but just claim a town and hang out there. I personally like to chill in Yuno, and various other guilds have "headquarters" throughout the world. Inhabit a place, don't ask the GMs to design a new one.
make a few lil maps - As pointed out above...as far as I understand this would be a great deal of work on top of everything else already implemented.
that can be rented - This would require new scripts as well I assume, though they may be similar to already-existing scripts. Either way, even more work that does not need to be done.
I will agree, this would be a really cool feature, but is the actual utility of this feature worth the massive efforts that would be required to make it happen? I mean, we only have one castle open on each map more. If/when heRO grows that much more I'm sure more will be opened. For now just enjoy the game as is and take over a town.
P.S. Yuno is mine
P.P.S. I'm not trying to drag you down, and I'm sorry if any of that sounds offensive.