Lack of custom protocol support troubled me as well, so I implemented it. You can find a full discussion of my questions and implementation at
viewtopic.php?f=25&t=817. I keep a github repository tracking my changes at
http://github.com/jonmmorgan/wxwebconnect/, which includes the protocol handler and a number of other changes I have found useful (Though please bear in mind that probably all of the features I have added are still not production ready and can be difficult to build because my application using it is still not so ready and so I have done more experimentation than bulletproofing. When BPBible is going into alpha or beta I'll be more motivated to bullet-proof the changes).
As for X64, I have not really thought about it beyond knowing that our users already complain that the existing version doesn't work on X64 (using wxHTML), and it sounds like this isn't going to change with WebConnect. Just out of interest, are you aware of
http://wiki.mozilla-x86-64.com/Main_Page? It looks like this has X64 builds of Firefox and they work (also Mozilla nightlies now have X64 builds for FF, though apparently not yet for XR - no idea why). I don't know whether wxWebConnect would work with an X64 XULRunner or not. Also, even if XR 2.0 final comes with X64 builds for Windows I suspect XR 2.0 won't work with WebConnect without some changes, though I can't say what they would be at this point. Making XR 2.0 work will probably move up my priority list once it has been released, because it should have lots of lovely performance improvements that are worth having.
