Wired, I think you have things a little backwards. The enzymes in the mash don't do anything to the sugars other than MAKE them, from starches (I know, over simplification, but I think you'll see my point). Once the sugars have been made from starches, whether in the mash, or with crystal malt in the initial stages of wet kilning, they are pretty much set. They will not change again until fermentation. If the enzymes made short chain sugars, the yeast will eat them up, if they made long chain sugars, such as malto-dextrin, the yeast will leave them alone.
I suspect the difference here between Munich/Vienna malts, crystal malts and caramel malts is the ratio of short chain sugars to long chain sugars in the finished product, hence the difference in residual sweetness in the beer.
I would suggest large percentages of Munich or Vienna (cara-vienne or cara-munich may also work, but not in as high a percentage) to get what you are after. I find it gives my beers that slightly sweet toasty/bready character without being too sweet. Both Munich and Vienna are self converting, and you could use them up to 100% of your grist. I did that with a homebrewed all Munich (5% cara-Munich) beer. It tasted great, with a nice rich bready/toasty character. Great teaching tool to show people what Munich adds to a finished beer.
-Lyle C. Brown
Camelot Brewing Co.