Right now guild dimensions are just larger in the amount of items that can be placed into the dimension.
Until they add in furniture like Manniquins, Wardrobes and stuff that can add in storage slots these are just Eye candy an a place to run around on your own accord. I would even like to see the ability to have trees that give off wood weekly, plants to grow as well. Have a rock formation for ores. something along the line that items taken care through the week will reward crafting items. but for now eye candy is still a good start in this aspect.
I know how to create one and build in it but how would the leaders go about starting a guild dimension up? Also I see that at a particular rank we can have more than one, we are at the lowest rank for now and I would like to upgrade later but as of right now I will beautify the first one. Does this mean I am wasting the Plat on the first key when there will be better dimensions once the guild levels up? Or...could I level the first one up spend the 200-500P for a key then when our guild levels there wont be different options, but the same options available as long as I have the money?
not all sure about the guild ones. though I do know they are availble to unlock with price once you reach the level restriction. and they would set the restrictions through the guild ranks for members on who has access to do what.