Obviously, it is quicker and more efficient to use a large bulldozer and, unless you have one, that means hire one. I think that most folks who can afford to own a CUT, FEL and BH can probably afford to hire a bulldozer if they want to. However, if you're not that concerned with speed and efficiency and have the time to use the project to hone your skills with FEL and BH, it can certainly be done.
I have been doing exactly that with my
B7800, FEL, toothbar and BH. I am almost finished excavating a landscaping pond that is about 80' long, has an average surface width of 15-18' and a max depth of about 7'. The width at max depth is about 6-7'. I worked on it for a few weekends (total of maybe 4-5 days in the aggregate) in the fall and then resumed after the ground thawed this spring and have put another 2-3 days in. I expect to be finished with the rough grades and drainfield and ready to drop a layer of sand prior to installing the liner in about another 2 days of work.
BTW, pretty much all of the excavation has been done w/FEL and toothbar --I have only used the BH for digging out around some humongous boulders that I encountered (see my post in Projects on moving large boulders /forums/images/graemlins/grin.gif ).
Along the way, I have had a a lot of enjoyment and am a lot better using both the BH and the FEL than I was before this little project.
So I don't think it's impractical at all; just an individual call as to how you want to spend your time. On sunny Spring and Fall weekends, I'm pretty happy spending mine running the Megabeast. /forums/images/graemlins/wink.gif