In-line semi's turn in to in-line pumps, which are looooong. Often uncomfortably long.
I've seen one or two bolt action conversions which turned out rather nice, which is of course nearly the same as pump, just with out the added length of the pump arm. Solves that length issue. And heck, after a little file work on the feed port opening you can flip down the feed neck and single load First Strikes.
Though it might be a challenge, mill off that front grip and rig up an undercocking setup with the pump entirely under the front of the body. That could be sweet.
On the other hand, one alternative is to build yourself a Back to Basics gun. You got a nice simple, reliable, mech blowback. Ain't nothing wrong with that. So when you show up at the field and nearly everyone is using rentals and blowbacks you have your own to pull out of the gear bag and maintain an equal field. Of course there's no reason you can't make it a Nice, reliable, mech blowback. Stick an on/off ASA, a decent barrel of your preference, a swanky new set of grips, and maybe a good reg to smooth out the chrono readings.
David Johnson, AKA Fubarius.
000110 200 11202 10 000020
012211 021 22110 22 121101
222001 222 10220 00 022212