Why not just speed augment your glaive? There's a tradeoff in damage, sure, but you still get the range (and mathematically, the damage tradeoff should work out to an equivalent DPS, just without getting hit twice in a row every other turn while waiting for your glaive).
No, I think it's worse than just transmuting into a greatsword. The game doesn't agument proportionally, it just multiplies one by .66 and the other by 1.33