Honestly Lap bars wouldn't save the coaster, its the track (mainly because the ride is built on reclaimed land which has settled over the years) track creates the roughness, new trains would help for a few months but wouldn't save it, really what they done so far (walls and concrete around support bases to reduce any more settling) is the best they could do without replacing the whole ride. Similar situation for Saws sudden left then right neck snap at the bottom of the main drop, can be fixed easily
personal opinon if you want to make Colossus less painful, just wrap the restaints and seats in foam padding, help alot
Also main reason looping coasters don't have lap bars is because the GP are not used to that idea. It be perfectly safe, but the public would be nervous as there used to over the shoulder for anything going upside down (you would get a similar fear from the GP if a inverting RMC appeared in this country)
Also first post