I pre-tied all my "Jig n teaser" cod rigs already as follows:

50# big game mono
One end is an "end loop knot"
18" up is a dropper loop with 5/0 Gami Octopus for teaser
1 foot up from the dropper is barrel swivel

I plan to attach the jigs on the water like I would a sinker - through the loop, easy. This also makes for fast changes. Will this kill the action of the jig? Should I just tie them on with a clinch knot when I'm on the water?
Problem with that is the rig will get shorter and shorter as I cut and re-tie...

Any suggestions?

i use that sometimes, i also like using a big snap like spro the snap it self is like 2" long. i wouldnt worry bout killing the action.

use a big coastal snap like berkley or sampo. thats the standard rig u made. it reduces the time of trying to fit the jig into and outta loop.

these dont affect the action? and what sizes of the snap?

hey, u can tie the jig directly to the leader or use a coastal lock snap for 175 lbs.

cod fish are not to leader shy so it really does not matter.
Your just jigging up and down there is not all that much action. I use a big snap swivel for quick changes.