Just an update for anyone who ever stumbles across this.

I ended up installing SABAYON XFCE and after a lot of fiddling,
most importantly changing the window management
off away from xfwm onto metacity (--replace)
I have a completely useable touch-screen tablet,
running a proper linux kernel.

It runs quite well our industrial repository software,
and being that it has a battery (about 4 hours lifetime under load)
does not need a UPS to support it (unlike our other gear)

I still want to get the HUAWEI em770w to make telephone calls
so our operators can can call up for assistance or whatever,
but maybe there is another way to do that.

cheers from the bleeding edge....


PS:
WAMMU-GAMMU still seems the easiest path for making phone calls
- it does not require an endless regression of dependencies.

I actually got WAMMU to call using a different HUAWEI modem
but need a bit more time to find a way to trick the audio through.

If I can crack that, then no need for something special,
like most smartphones,
assembled and sold by a bunch of pawns
owned and manipulated by the oligopolistic triad.

...Just carry a linux desktop in your pocket