There is nothing wrong with a square taper bottom bracket, I would disregard that suggestion. If you actually saved any weight, it would be expensive.
If you really want to save weight, you can probably still get a square taper TA Axix titanium axle unit.
I wouldn't bother on a full size bike, but I do have these TA units on the 3 family Bromptons. I care about weight on these as I often have to lift and carry them.
Downsides of TA Axix titanium:
- price (but I got mine relatively cheaply with a good deal from my LBS).
- might be a bit more fragile, though not broken any axles yet.
- axle/crank interface needs more care than with a steel axle, either Loctite or more frequent checks.
Good point of all TA Axix units (steel and titanium):
- bearings are standard industrial units, easily replaced, easily available from online bearing sites, and fairly cheap. I bought a small stock of these, in addition to the titanium version on the Bromptons I also have the steel version on some of the full size bikes.