Your project looks great. I appreciate that you've spent so much time on it. However, what I'd be after is an independent mobile theme. It seems a lot of suggestions for a good functional mobile vBulletin 4 theme would involve breaking the functionality of the main themes and only using the responsive one.
The main theme is very important to my forum, so having a separate independent mobile theme would be mandatory for me, but it seems I can't have it both ways. Fortunately, my members are satisfied with the BYO Tapatalk app that I offer. Sadly, it wasn't all that long ago when Tapatalk was talking about possibly having to axe the service at some point. I want to prepare for that and give my members a second way of using my forum on mobile.
The only other apparent option is a full move to XenForo (or an alternative), but I'm not going down that route. I've invested too much into vBulletin 4 and I don't regret what I've spent. Aside from a couple of problems like this I've been very happy with it.