Wouldn't least effort (software-wise) be replacing the touch screen with dual touch one (if its more or less the same price) and connect it with some hw hack (like you wrote) but in a way that it would treat the first touch in a same way as it does now and just ignore the second finger? It might require a crippled kernel driver at first (reporting only the first touch further to the software chain), but then hey - we would have multitouch high-accuracy resistive sensor which would not be used by Maemo at first, but could be used by other systemas... and some future post-release Maemo software patch/update (fully-featured kernel driver + x11 + gtk + hildon + qt) could EXTEND the current event system with additional events for second touch - so current apps would just ignore multitouch and react only to plain ol' single touch, but new apps could be written (new apps - yeah, I know ).

In fact, I don't need the multitouch and statements like "But for a 2013's project at least a dual touch is a must." even make me laugh and smell like an Android/iOS ad, but I do see a potential in it and wanted to point my idea out (probably it was born in few others' heads as well, it's quite simple).