I've used this junction a few times since moving to Biddulph in August 2013, and it's not at all nice. The southbound slip roads are fine, but as you've rightly pointed out, it's the northbound ones which are awful. Even in the small car which I drive, I feel they're too tight, so they must be pretty bad for HGVs! If the northbound slip roads were changed so the curvature weren't as tight, then accidents could be more easily avoided, although there's the A5182 bridge over the motorway just to the south of the junction to take into account.
With regard to the roundabout, there's always the possibility of making the junction more free-flowing by constructing a flyover, which would be ideal for traffic coming off the M6 northbound, but traffic exiting the M6 southbound may have fun trying to weave around in the short distance before the roundabout. With good lane markings and decent signage, this could work well. Coming westbound on the A500 and heading to the M6 in either direction shouldn't be too much of an issue either with a flyover, but traffic using the roundabout to access the M6 might have the same weaving issues as traffic coming off the southbound M6. However, given that traffic exiting the roundabout heading westbound will only be going to the M6, that may not be as much of an issue as first thought.
I'm sure there are other ways of making it more free-flowing while still keeping local access in, but this is the first time I've ever really thought about how to improve any motorway junction, so I'm a little inexperienced!