If you're running an older mid 90's cocker that was meant to run on direct CO2 I think you'd be OK using a bottom line to an expansion chamber. Not just a feed through but a proper multichamber expansion chamber. I'd still not want to go with it for really cold temperatures but down to maybe 50F I'd think it would be fine.
And running a larger 16 or 20 oz tank will give you more surface area for the CO2 inside to recover sooner by allowing more of the outside temperature to feed through the sides into the CO2 inside.
And I'd run an antisyphon with all this just as an added level of gas only security.
Regulators? PHTTHH! We don' neeed no steeeenkin' REGULATORS!....