First question you HAVE to ask this guy- did he use super glue to assemble the plastics? Or did he use plastic cement? Hopefully since there are metal models he used super glue for all of them- but it always good to ask rather than getting stuck with figs that are ...well....stuck...
Please do NOT put acetone on plastic figs- acetone can eat though some stryrene plastic mixtures faster than super glue you want to dissolve(
GW styrene plastic mixtures have not been consistant over the years)
The easiest- and safest way to remove the paint- AND- super glue, is SuperClean (
http://www.superclean.com/index.php ) This works better than simple green for stripping and dissolves super glue in a couple of days when cold, less if kept warm. Doesnt hurt plastic at all- and is safe for metal if its only left in there for a week or two (long term it stasrts getting nurglified). Drop them all in a bucket or large bowl for a soak and they all just sort fall apart when you brush the old paint off. I'd recommend keeping them sorted by bug type to keep their bits from getting all mixed up though.