I do enlarge colour slides to b&w, and I like the result, starting from Fuji 64T or astia etc. Velvia is the hardest! Anyway, there are some very powerful things you can do in terms of filtering to manipulate the tones. You will probably want to think about how you expose your chromes; preflashing may not be a bad idea.
So far I have been enlarging to 5x7 tmax. That has worked well for me. If you aren't going to use a pan film then of course you will need to filter as you shoot to avoid tonal oddities in the reds. Whites can be blotchy if you don't dupe to pan film. Ortho didn't work for me at all....
The other thing you can do, of course, is scan and have LVTs made, with whatever curve you like. Chicago Albumen has done some of that for me, with results that I like very much.
(Now, I know that some here will regard LVT as some form of digital, but let me just say, LVT was a tremendous resource for film shooters long before digital, and the result is in an entirely different league than what you get from digital negs. LVT is something that we film shooters should be fighting to keep alive IMHO)