Stupid 53 question of the day: Wouldn't you get some benefit if you just removed all the retraction mechanisms? Or does that become a weight and balance issue?
About all you'd save on weight is the weight of the hydraulic actuators and some associated plumbing, but not any heavy structure from the struts themselves. Saving weight is really important in helicopters, even more important than fixed wing, but-
(and I'm spitballing here- I'm not a 53 guy) I think the weight of all that stuff is probably about fifty pounds, which seems like a lot of payload to be wasting on every single flight- but consider it's also about how much fuel those things burn in one minute.
Any effect on center of gravity would be a wash. The mains, which have the heaviest components, are close to the c.g. The nose gear, with lighter components, is proportionately farther away.