It's easier than you think, you can program the default out bound SP# on each Obi1032, so the desk phone user doesn't have to choose a line to dial from. They can just hit speaker phone, or start dialing numbers and press "DIAL" and the Obi1032 will automatically dial out on their predefined SP#. (I have my Obi1032 set to always use SP2 for my outgoing calls). Each phone can be setup independent of the others.
For the sanity of your person attending the phones: Program your other devices as speed dials off the seven programmable keys [side keys] (reserve the top Programmable Key as "Next Tab").
For example:
(2)=Your Cell
(3)=Your Obi1032 Desk Phone
(4)=Employee 3 Cell
(5)=Employee 3 Obi1032
(6)=Employee 4 Cell
(7)=Employee 4 Obi1032
I'd put this same key programming on each Obi1032 in your office, so that if your attendant is standing at anyone's desk, they can answer a call in the same manner as they are accustomed to at their own desk. You can easily print out little button labels, and cut them out to fit under the plastic cover. On the Obitalk expert page, its at the bottom of where you setup the programmable keys.
My attendant is using an Obi1022, and literally hates how difficult it is to transfer a call. I plan on putting a Obi1032 on her desk with the programmable keys setup in the manner above.
Alternatively, you could just have each GV number for each employee ring simultaneous with the respective employee cell, and the employee could choose what the best device to answer the call is. (There are times in my office when we're about to run out of the office, and we'd be fine taking the call on the road with us on our cell, if it had been forwarded there to begin with). Then you'd only use three of the programmable keys, and have room for adding more employees in the future...
