Interesting, I would never have known this. (Then again, I don't have a self-cast modifier)
Hurray! I looked at the LUA but I'm not that good at deciphering other people's code. ;). My mod to the (original) Flexbar was about as far as it went (and I do programming for a living!)
Also, another little buglet I forgot to mention: When a button changes states between a autocasting pet action and an 'empty' standard action (possibly other varieties of standard actions as well, did not test), the autocast highlight sometimes stays on.
The inability to have alt page AND be self cast, is the sole reason this is not my main button mod right now. (I have a self cast bar, that pages!)