For your own safety disconnect the battery before removing the seat, remember its classed as a pyrotechnics device and will quite easilly break limbs or worse if you get them in the wrong spot and it discharges.
Essentially it will throw the SRS fault/light, it shouldnt stop the rest of the system from working nor should it create a limp home mode, best talk to a dealer and ensure they can turn it off if you want to permanently replace the seat.
Your essentially just creating a fault via a faulty airbag (it not being there) so i cant see it too much of a big deal unless your in a bad accident
For the weight and issues, maybe just look at some sort of 4 point racing harness or similar to hold you to the seat, giving enough room for the airbag in the seat to discharge if it should ever need to.