Hi DTree,
Nice looking cedrus with the big bonus of a good base and taper it seems.
Have had some experience with libani and deodara and also killed off a large deodara Golden Horizon with bad soil and overwatering. True cedars are, after all, high desert trees generally speaking (Atlas Mtns & Himalayas, Lebanon/Jordan etc) so need a gritty, fast draining soil mix.
Beware of removing lower branches until you have decided on a final height and branch arrangement as I have found them reluctant to backbud or sprout new branches out of nowhere on demand.
Branches with existing foliage, however, bud well after pruning rather akin to a larch.
I've got a deodara glauca ( a smallish one) and I can prune back the branches to the last 2 or 3 sets of buds and get new budding but suspect that, like a pine, you never prune past the last set of buds or will kill the branch.
I would suggest that you will need to reduce the height of this tree to somewhere around the red line and there seems to be the beginnings of a tree shape in the vicinity.
How to reduce it leaves 2 main options - either chop to a side branch to form new leader or jin the existing top al la St. Brent Walston linked here
http://www.evergreengardenworks.com/cedars.htm
Like Mark said, the foliage on a deodara isn't as bonsai friendly as libani, bevifolia and atlantica types, but on a larger size bonsai could be manageable.
There's some decent examples shown in a Google image search for "cedrus bonsai" but not a lot.
Hope this helps.
TimR