Sounds like you are heading in a good direction, the sky is the limit more risk more reward, Like MarXtar said some methods could be dangerous, i've seen people with systems left in provisioning tasks get accidentally rebuilt. And depending on security you might not want sales people to accidentally install an admin system at the sales site?
I would need to hear more about your environment to really give you sound advice, some paths will lead you to more admin work to keep it working down the road, some paths are easy to set and forget but less agile. You said you have multiple PXE reps on multiple subnets do they have replication setup or act as preferred servers? Does this need to be fully automated? How many apps are there per build and are the apps already packaged in LANDesk? It all depends on your environment and that is what is so great about the product.
If you don't know where the system is going to end up but you have someone able to interact with the build:
You could invoke end users action with some custom scripts during provisioning. If someone is building these systems and pressing F12 or what not to PXE boot could they also be prompted to enter / select sales service or admin so you could target a new system with deployment packages it deserves.
If you know the MAC of the system and if you know that specific the machine is going to be for Sales you could assign it right to Sales provisioning template.... right?
Another option could use query targeted tasks to bring the generic system to a customized state using software deployment task or user based deployment model....