There is a major lack of coherent communication in regards to merged mining. I'm willing to implement it if there were some central location that information were able to be found... but so far you have to comb through various posts and forums that are disjointed and inaccurate.
But as of right now, it seems that the only information that I have found is that it's unstable, untested and almost unusable without a lot of trial and error.
Ill parrot part what some of the other ops have said as well. Mainframe is looking into this but not jumping in with both feet for the following reasons:
1) unsure of demand for this from miners
2) same reasons Inaba mentions (lack of coherent and centralized information)
3) same reasons Luke-Jr mentions. Im also not willing to jeopardize a stable BTC pool with unproven merged mining code (unproven in a live full scale production environment)
If some of these issues are addressed im happy to look at implementing it as well.