which is why we don't have any SE unpressurised turboprop IFR tourers
Doesn't the turbine SF.260 come into this category? Not that I know much about this, but the certified SF260s are IFR capable so presumably the same applies to the turbine version. I guess that there may be other reasons why you would not tour long distances and don't know what their endurance is, given their design as trainers.