You say it would be wonderful but do not provide examples as to why. Why would it be wonderful? What would these players, with their extra disposable income, be paying for? Why would they want to pay a premium fee to play on these special servers? How does creating a gated online community help increase sales or improve the profitability, if there are no benefits?
The game already offers additional features such as extra retainers, name changes, appearance changes, and optional items from the Mogstation for those with disposable income to spend on. You can always create your own exclusive fellowship, FC, or a LS to have your own gated community without even having to pay extra.
If you have not thought it through, then it is merely a whim and not a serious request by any means. Either that or you only want to see the reactions of those who would be excluded.