I make cabbage-pork sausage all the time... but as the filling for gyoza or pot stickers!
All the points above on getting rid of moisture are true. Cabbage has a ton of water, if you've ever made kimchee you'll know. The instant you put it in contact with salt, it starts to weep water in huge amounts.
When I make pork-cabbage sausage for the filling on pot stickers, if you don't get it folded up in the skins and frying within 5 or 10 min of adding salt, you will be left with a watery mess.
Once you mix, with fresh cabbage, you are done binding. As the water weeps out of the cabbage, it won't go into bind with the meat as it sits, and you will have wet pockets around the cabbage, and a crumbly unbound texture. I have often wrapped a sausage sized chunk into an eggroll, and that is what I've found. With gyoza and pot stickers, you steam about 2t of meat inside the flour skins, so dripping moistness is expected and not a problem.
If I was goint to use cabbage, I'd salt and drain the cabbage extensively first.
I recently made a bulgogi sausage, and put chopped up kimchee in it, similar thing. It was OK. Everyone felt it would have been better as meat sausage with kimchee served on side. You're always gonna serve a sausage with something, so you need to plan on some kinda topping anyway, and where that topping like sauerkraut makes the most sense...inside or out.
Good luck, let us know how it turns out, hope my comments were helpful!
