The first question is an easy, Yes/No.
The second question is How?
Here is where the hordes of players doing computer studies or gaming studies can let their imaginations shine.
Do we unleash the player owned house servers a bit so that houses can be more free form?
Do we have small bitmaps of paintings that players can create in game?
Do we create an engine that players can pop into to design armour and weapons, which they can email to Jagex?
Do we have a monster cauldron that players can take set ranges of attributes and paste them on to a monster they did the art for?
Is it easier to start small and go large? Or design something that can do it all?
We have the beginnings in player houses and player dungeons. And Jagex can easily tell how much time players spend designing their houses. There is demand for player created content.
We know that also from all the posts over the years of players wanting to work at Jagex. And Jmods saying how much fun they had making games.
Again, Runescape is not the only consideration, Fun Orb also exists.
I know it sounds terribly hippy. But talking is how this happens.
The more players talk the more they will feel that they have power in the decision, that Jagex is taking them seriously.
The Hows are a whole world of variation, but they should all come from players. Assuming they vote to have player created content investigated by Jagex.