Firstly, you'll probably get flamed for admiting you like AoC but to give you support (and to be flamed too) I have to say I enjoyed my time in AoC as well.
I would have enjoyed it much more if I had an ISX to go along with it. While the game was in beta there was a team working on an ISXAOC, they were active in IRC and had a website going. Sadly the work was never completed. After the initial fall of the game's popularity, the guys making the extension quit and that was the last I heard.
Anyway, so to answer your question; no, there isn't an isxAoC. But yes it's been considered. Perhaps Amadeus would be willing to write one but I wouldn't task him with that. Not with Final Fantasy XIV coming out and all. That's the one I'm going to be asking for
