Ok, I’ve looked at this a bit more, and think I have the only viable solution for you,
What you want is the rotary drive, which has an output shaft with a chain gear on it.
You will need a properly sized flat chain gear, with the same pitch as the gear on the rotary drive.
What you will do is drill 3 (or 4) holes in the flat gear, and drill & tap corrrsponding holes in the rudder arm. You will now have a chain gear mounted on top of the rudder shaft.
On the port side of the floor well (about 1/2 way up) you’ll drill 2 holes.
In the port cockpit locker is where the rotary drive goes.
When you do the install, mount the drive on threaded posts. That way you can adjust its mounting base height exactly to take the exact amount of slack out of the chain required.
Some notes.
You will definitely need the gear and chain to be stainless.
You will need to figure out the size of the gear through calculating the hard over times from the drive. The way you’ll get this is from motor rotation speed, and work backwards. Raymarine can give you the rpm on the drive.
You may choose to replace the gear that comes on the drive with a different size depending on calculations
As the holes on the side wall will be well above the floor, you shouldn’t get any water through the holes.
The rudder reference is waterproof. There is plenty of left over room in the floor space to mount it.
I really think, with the setup you have, that this is your only option for an inboard pilot.