I am about to ask such a stupid question, because obviously the answer is if it was possible it would have already been done - but is it possible to make a coma corrector that is telescope focal length specific, like one for f3.3 and another for f4? Like the way that some field flatteners are made for specific telescopes? If possible would that cut down on size and weight vs. the paracorr?
A coma corrector can be tailored to a specific f/ratio to correct a certain size of field.
But how coma correctors work is that they correct coma at all f/ratios, they merely correct certain sizes of field down to a particular f/ratio and then correct ever smaller fields below that.
In practice, people with newtonians longer than f/6 don't use coma correctors, so having a coma corrector be useful from f/3 to f/6 pretty much covers the range.
So if you want to correct a 40mm field to make it free of coma, the Paracorr II will do so down to f/3.5, whereas the Paracorr I will only do so down to f/5.2 (estimate).
If you, on the other hand, only need 30mm of field to be corrected, both Paracorrs will go down to even shorter f/ratios with full correction of coma in the field.
Some of the size and weight of the Paracorr, which, by the way, is lighter than the Explore Scientific HRCC, is due to the tunable top that allows all eyepieces to be focused (so the Paracorr stays in the same place in the light cone for all eyepieces)
and can accommodate a wide variety of eyepiece focal plane positions. If all your eyepieces were parfocal, the top of the Paracorr could be a simple drop-in tube, like a Barlow, which would make it smaller and lighter.
If you only wanted correction to f/5, for example, it could be simpler and lighter. If you only wanted to correct 1.25" eyepieces, it could be even smaller and lighter.
But, if Tele Vue is going to sell a coma corrector, it needs to be usable with their eyepieces, and a lot of other eyepieces to make it useful for people who have newtonians and sets of other brands of eyepieces.
And that constrains how it is made and how many lenses it contains, and thus the weight and size of the CC.