I don't have any experience with a Paracorr, therefore I have to ask:
Does its optical design leave space for a filter slide between the top lens and the eyepiece barrel (using the lower setting)?
This is not about the existing housing, only the optical design. Looking at the pictures it seems that there is enough space.
The paracorr has a filter thread, which allows to exchange eyepieces while using a filter without swaping it from EP to EP. However, I guess that adding a piece of glass in front of the Paracorr requires repositioning it. Please correct me if I'm wrong. If the filter stays between paracorr and eyepiece, it only requires tweaking of the tunable top, which should be easier given what I've read.
For me, the ideal would be that the Paracorr housing had a filter slide and a collet type mechanism (e.g. Clicklock) instead of a compression ring. I love the Baader clicklock and the Baader UFC (filter slide) - both used in a SCT and a refractor. Maybe TV should give just the basic optical cell to Baader so they can engineer something around it (dreaming...). Baader has a coma corrector but not really practical for 2" eyepieces.