I don't think it would be a problem. I have a 15.6 cu ft freezer (not converted yet) and it is certainly deep enough for cornies. It looks like it shouldn't be a problem to run lines to a tower and keep clearance from the lid.
MATT - 65g in 2k8
3rd Circle Brewery
Ferminatin' - Route 666 Pale Ale
Figurin' to do - Oatmeal Stout, Gueuze, Belgian Blonde, Mild, English Pale Ale, Weizenbock