Intamins are some of the smoothest coasters on the planet. They age better than b&ms, which all start to rattle after about 20/25 years. their looping coasters almost all have over the shoulder restraints. Some of the newer ones have these wider things that are more like handle bars but that is rare from them. They build a lot of very intense coasters, and that's their specialty. While millennium force, a giga, has a lap bar and doesnt go upside down, their newer coasters are actually so intense, like Intimidator 305, that they too have over the shoulder restraints. See also anything they do at Ferrari world in dubai, Maverick at cedar point. They built top thrill dragster with lap bars but then kingda ka, basically the same ride, with over the shoulder restraints. skyrush at hersheypark has lapbars but also a completely different track configuration and some of the most intense and painful negative Gs on the planet. Superman: The Escape used to have lap bars. when they reversed the trains, they installed over the shoulder restraints.
Some coaster manufacturers are making looping coasters without over the shoulder restraints now. B&M is inching their megas into inversion territory only slightly with overbanked turns, and Rocky Mountain Construction has lapbars with shin guards for two points of contact as well as seat belts. The load time and capacity is hindered by having to check 2 restraints on those rides.
Long story short, the trains for screamin/incredicoaster are fine. They were designed for that ride and while the industry trends toward ditching shoulder restraints, intamin hasn't; they've actually put shoulder harnesses on ride types that typically don't use them. The trains fit the track like a glove and after almost 20 years, the ride is still incredibly smooth. Its banking is perfectly calculated so that for the most part, you are pulling perfect positive G's and pressed into your seat rather than side to side. There isn't any head banging so no major reason to get rid of the harnesses. No need for new trains other than a desire for a new style. New trains could be smoother and more trustworthy because they are brand new, but that doesn't mean they have to be a new model of train. Vekoma and arrow dynamics' trains' wheels dont even fit on their tracks, which is why the trains bang around so much and transfer those collisions to riders heads against the shoulder restraints. Not only would vekomas space mountain: mission 2 trains not fit on intamin track, they would likely be way worse for the guest comfort.
Finally, I'm fairly certain the loop was completely replaced. Disney actually announced that they were changing the launch and the loop, that isn't speculation, and it isn't the same as them removing it to modify the circle backdrop on screamin. I've always noticed that the loop was super rough and rattled. The loop could be identical, which would indicate that it had just surpassed its life expectancy (which doesn't make sense, given that the rest of the ride is the same). Incredible Hulk at IOA was completely retracked and dueling dragons thrown out this year because those b&ms, in daily operation with no off season, hit their life expectancy. (Most older b&m's at regional parks have seasonal operating schedules so they don't have to come down.) It could be that they modified the supports or the track profile to de-stress it. That loop was always actually very forceful, even for traditional vertical loops. It has a pretty stable diameter, and this could have been done to ensure that riders would still be experiencing positive G's at its top to so as not to scare them, but it made the entrance and exit of that loop pull really intense positive g's. I thiink they might have made the loop taller to give riders' bodies a moment of rest at the top before they level back out, the way arrow dynamics intended for vertical loops to feel when they started designing more of them back in the 70s.
