Like flyangel2, I have worked as an office manager and bookkeeper at a DZ, and I know the difficulties of keeping track of everything at the end of the day. A DZ has the responsibility of paying for the packing of the Tandem and Student rigs because they own the rigs, and therefore, it is a necessary expense for their business. Video guys and AFF instructors are solely responsible for the packing & maintenance of their own rigs.
If the DZ paid for your packing, it would still be considered income to you because the DZ does not own your rig. You therefore will still be taxed on the full $40 for video jump, and would not be able to expense out (deduct) the $5 for the packjob. It really does not make sense for the DZ to pay you to pack your own rig. Please know that I really do understand your logic, but the fact that it is your personal rig is the reason behind the bookkeeping of the DZ.
A DZ needs to stay inline with taxes & rules & such in order to keep their business rolling, just like you do. You truly cannot control how a DZ handles its books or operation. (And packers are responsible for their own stuff too.) The only thing you can control is your own Video Business. The fact that you are questioning & researching for solutions is great! Please keep it up - it will definitely help your business grow!
Here's a little more advice. Remember to always record all your expenses. For the packing expenses, either keep a good log or have the packer give you a printed Invoice. Both jb092 in the above post and Keith Larrett (Visual Expressions) always made sure that they got a printed Invoice from their packer. Also rehmwa idea of having the packer sign the log is a good idea. You can either have the packer sign each day, or sign a generic form stating that he/she certifies that he/she has packed for you on the dates recorded in your log.
You are taxed on NET PROFIT on Schedule C, which is INCOME minus EXPENSES. If it is a valid expense, dude, record it!! That means video tapes, film, tools & stuff for your helmet & jumpsuit, office supplies, shipping charges, non-video jumps are your training jumps (be reasonable though!), USPA dues, etc.
Take care, and stay true to you & your dreams!