ah yes the selling bug....
found it a day ago and it's been fixed (You can fix it yourself too - open the SOW folder and open the file "SOWVLSell.sqs" - search for variable "_cuVQTY" and change it to "_curVQTY" by adding the "r" then re-export the mission)
I made up the price list based on value of weapon in the game versus an "actual" price... it was only to show what could be done - you can certainly set your own prices!
Locations you can pull any vehicle you want anywhere - It is designed that way to provide maximum flexibility for the mission designers. You can script your own way of keeping helicoptors on the pad and such if needed, but if you pull a helicoptor into a hanger you may not get it out - in result - no one pulls helicoptors to hangers! ;D
The storage container set up is explained in the documentation I believe but you can email me if you have more problems - I am happy to help.
It IS possible to log vehicles into locations without ending the mission, however, it would take an extreme amount of time for the server to grab all the vehicles and in turn transmit the data to the clients right now. Hence, why it is at the end of the mission - only the server does it because only the server saves the data! I will keep this idea of yours in mind because I plan on streamlining the vehicle "grabbing" code and eventually it might be able to be done on an individual location basis.
A fellow by the handle TREKKIE I met in the official forums has started making a Team v. Team v. Team version of this. His idea was to put locations at several bases and any team could take over the bases and gain ownership of the location AND whatever vehicles were stashed there - is a bit different but along the same lines as your idea! here is his website (its all in German though):
www.ofp-zone.de maybe you can swap some ideas?
any more questions let me know!