With no topcoat at all your decals would just fall off. They would look odd. Even for a wall hanger there would be no way to clean the bike.

Modern bike painters, the good ones, achieve final finish by wetsanding and buffing the whole frame. The last thing they want to do is buff into the edge of a decal. So they bury the decals and graphics in a lot of clearcoat. The 'no edges here' look is also more "perfect" and guys who pay top dollar for custom paint mostly want perfect.

Nearly all De Rosas and Merckx will have clearcoat. You can see edges because for production work, even De Rosa level production work, it would be too costly to do it the way repainters do it. Just one or two light passes, easy on the buffing. Early De Rosa would have done something else. I do not have a rack of pre 1970 De Rosas to examine for clues.

Imron was introduced 1970. Good enough and easy enough it changed how bikes were painted pretty quick. Before then there were other ways to do it. Probably more ways than I would know. Most basic was to varnish the decals. On some bikes you can see that varnish or what is left of it. The simple way to make varnish that was very thin, very durable, and amazingly easy to brush was to use lead. No brush marks with lead. Lead was legal everywhere for this sort of application well past beginning of clearcoat era.

It is only new once. It is only original once.

You could try asking your painter to do it the factory way, light on the clear. To be much good as a painter requires a lot of obsessive-compulsive behavior so don't expect them to be eager to do it your way.