^Couldn't Beatty just be an executive producer on a film made by someone else?
The problem is that Beatty is an utter control freak. That's why a movie like Love Affair, in which he was nominally just the star, ended up running massively behind budget and over schedule - he kept re-writing Robert Towne's screenplay and telling Glenn Gordon Caron how to direct it. A simple love story ended up costing as much as most SFX blockbusters thanks to him. So I wouldn't be hopeful of him doing the decent thing where Dick Tracy is concerned.
PS - my choice for a live-action DT? - Chris Noth. Looks exactly like the f*cker!