I think the key factor is POSSESSION. If fish are at a licensed processor, until they reach your home I believe the reg considers that those fish are still possessed by you. While that may be the technical interpretation, of course it would be nearly impossible for enforcement folks to pursue such a situation unless they set up surveillance, which would be highly unlikely unless they suspected someone of grossly abusing the system. I think as rec anglers navigating the regulations we also have to realize that the regs don't cover every eventuality, like what if you took your fish home and then from home to a local processor to be smoked - do those fish become part of your possession limit, a second time, until the processing is complete and you get the product back home (and what if that takes months)? As with most fishing regs, they are written to stop intentional poaching and to prevent poachers from getting off due to loopholes but can't cover off every possible scenario.
With regard to the OP, I do believe that some, if not all, licensed fish processors are allowed to ship your fish to your residence while you are still on your fishing trip and once the fish they've processed and shipped reaches your home residence, you are free to harvest more fish. On the surface, the cost for such a service may not seem worth it but, given the current price for fresh halibut, if you were into some good hali fishing and had room on your license, it may be worthwhile to ship home your first couple of fish.
As I've said many times on here, with an annual quota of just 6 halibut and a desire to stretch the rec allocation across the entire season, traditional possession quota doesn't provide the best solution for all anglers. With the requirement to record your catch it would be easy enough to set a daily, monthly and annual quota. The slot limit, even though its never been proven to have any impact on harvest, could still be implemented as part of the monthly and/or annual quotas - say no more than 3 of the annual 6 fish can be over a certain size limit and/or no more than one or two "overs" harvested each month. Locals would still have access to a lot of halibut meat over the full season and travelling anglers may get a bit more flexibility.
Cheers!
Ukee