In re-locating a main service panel, every circuit will have to go into a junction box and new circuit wire run to the new service location. These junction boxes will have to remain accessible. That means no buried boxes, or splices not in a box. The easiest location for all these junction boxes is in the ceiling covered by a removable panel. Fire-proofing has to be considered also.
I wrote this a few months ago;
On my house here in NC, I wanted to build a garage to store my trucks & camper in, I had to re-locate a 400Amp service. Included in the job was reconfiguring one panel to serve a 200Amp transfer switch for a 20K water cooled propane generator and relocate the meter for the 400A service. The code had changed here which required main disconnects for each panel located outside & accessible to the fire dept. While the new garage was being built, we had to run the house of a 400A temp service.
So relocate 2 200A panels, install 2 main disconnects, install 1 200A transfer switch with a picky inspector (small town) plus we were living in the house, so everything had to work at the end of each day. I was also recovering from 2 major back surgeries done days apart. Doing this would require abandoning conduit runs to and from the temp service, while reusing the wires, as they were going to be under the slab floor.
The inspector required us to have a junction box for each wire amperage, 15A, 20A, 30A, 40A, 50A, 60A. He would not allow just a couple of big splice boxes for it all. He would not allow double romex connectors. The contractor fought hard to not abandon conduit, I was paying, what did it matter.
All the junction boxes had to go into the garage ceiling, which is a fire rated ceiling, thatâ€™s the reason I didnâ€™t like so many boxes.
Now about relocating a service for cosmetic reasons; The abandoned fuse or circuit breaker box, canâ€™t be used as a splice box, each and every splice has to be readily accessible. A route from the splice boxes to the new main breaker box will have to be figured out. The best one could end up with is a wall full of splice boxes instead of one big breaker box. Some wires might not be long enough to get into a splice box with itâ€™s brother so there could be splice boxes in the ceiling near where the old breaker box was.
It is not cheap to relocate a service, before I hired an electrician, I would hire one or several interior decorators, to deal with the problem in a more creative fashion. The box can be hidden by drapes, artwork or faux doors.