The way you described is pretty much what we in Comifornia has to do. I quickly read the Connecticut laws and its pretty much like here.
Let's say CZ just released a new scorpion version and I wanted badly. So I have to contact an out of state 07 FFL that can do the modification to be compliant. Then shipped to my local FFL to do the final paperwork.
I did a quick search about CT laws and I found is pretty much the same as the current CA laws.
http://lawcenter.giffords.org/assault-weapons-in-connecticut/Connecticut defines an ?assault weapon? as:
Any semi-automatic centerfire rifle, regardless of the date produced, that has the ability to accept a detachable magazine and has at least one of the following features: 1) A folding or telescoping stock; 2) Any grip of the weapon, including a pistol grip, thumbhole stock, or other stock that would allow an individual to grip the weapon, resulting in any finger on the trigger hand in addition to the trigger finger being directly below any portion of the action of the weapon when firing; 3) A forward pistol grip; 4) A flash suppressor; or 5) A grenade or flare launcher.
A semiautomatic, centerfire rifle that has: 1) a fixed magazine that can accept more than 10 rounds of ammunition; or 2) an overall length of less than 30 inches
Since California is a large market, CZ-USA last year or so started to modify (as manufacturer) Scorpion and Bren to be California compliant. The only thing that CZ-USA had to do was swap the mags, fixed the stock and made a fin grip. These are not shown in their website nor catalogue.
Here is a local Komifornia Big box gun shop. No pistol version since it not approved to be in the handgun roster (another non sense law)
https://www.turners.com/all-productsbrowsekeywordscorpion/browse/keyword/scorpion/brand/cz-usa08557 scorpion with extended handguard
08509 scorpion carbine with faux suppressor.
You may ask your dealer if they can get theses particular models for CA.
Again double check with your local laws. I just spent few minutes looking a them.
I hope this helps