A larger piston on the m/c for the same size caliper will give you a light switch on/off brake. Basically you will be moving too much fluid into the same size caliper.
A braided line is one of the best improvements you can make if you are keeping the stock caliper and m/c. Ken's suggestions are excellent - go through your brake system and make sure everything is functioning as it should be. Deglaze the rotor. Remember that regular Dot 3/4 brake fluid is hygroscopic and absorbs water over time causing corrosion. Cleaning and rebuilding the m/c and caliper along with fresh synthetic Dot 3/4 brake fluid will definitely help.
If you still hate the front brake, start looking at other single rotor set-ups off of more modern bikes - EX500, GS500, etc... Although then you get into having to make adaptors to mount the rotor, matching the rotor diameter to the caliper, etc... Maybe you can use a CB750 front wheel with one rotor removed? Geet? Any benefit in rotor size with this?
I've switched over to Brembo m/c's on a couple of bikes as they are much better performance-wise and the East Coast Brembo distributor is an ex-coworker. If this is something you are interested in, contact Fred at:
www.yoyodyneti.com
but you'll need to be able to tell him the current m/c piston diameter so he can match it up. Also make sure he knows you want a mirror mount and a brake light switch on the m/c along with the brake lever color (silver or black).....
Jim