Dan:
I've never been a fan of sharply uphill par-3's myself, for whatever reason, so I've probably never built a good one. Now I guess I'll have to start looking for one.
To answer your other questions more generally:
a) I don't know if you can change people's general nature about disliking certain types of features. I think you can override them in specific applications -- in other words, I'm sure there are some uphill par-3's that I would call great holes, but I still believe there are many more bad ones than good ones.
b) I don't know how I could have any more design freedom than I have, unless I were financing the projects myself. I basically have to answer to a single client, and as long as his prejudices and mine don't get in the way, we can build whatever we want. But nearly every client I've worked for has expressed some trepidation about some part of the routing or design along the way -- most commonly issues about the scorecard.
c) What sorts of holes would I design that I don't design now? It will take me a while to think about that one because I don't often think in terms of "blue sky" design. Generally, I'm reading a topo map and trying to fit holes to it, and even though I'm VERY good at reading a topo map, I think everyone has a tendency to visualize certain types of holes more than others. For example, Coore & Crenshaw build a couple of "up & over" par-4's or 5's on nearly every course they build -- Bill loves the downhill approach shot on those, whereas I have a harder time getting past not seeing where the tee shot is landing (and if there's anybody about to get hit up there). But, I do like the variety it puts into their golf courses overall, so I'm trying harder to find a place to build a similar type of hole.