Oh heck no, don't do that.
Imagine you found the perfect house. You love it too, but your partner also made clear that you that you weren't "getting any" except in that house's bedroom. Except, somebody concreted a 12-space FPE Stablok into reinforced concrete, conduits going through it and all. Your insurance company is saying, "If you want insurance, that HAS to go". What sort of choice four-letter words would you have for whoever who thought it was bright idea to concrete that in there in 1983?
Of course there will be no choice. You'll have to stick a new service and panel in an awkward and unsightly place, bypass that panel altogether, and rewire the entire house. And it's made of concrete, so the only way that won't bust the budget is conspicuous Legrand Wiremold all over the walls and ceilings. Thanks loads there, Humphrey!
If there's anything experience teaches us here, it's that changes to service panels are often necessary. Far beyond ordinarily "adding circuits", people have serious problems that require panel replacement.
- They find out they are dangerous Zinsco or FPE StabLok firestarters, that have to go.
- They find themselves with a Crouse-Hinds or Pushmatic that is inherently obsolete and simply cannot meet today's standards.
- It doesn't have those problems, but it's a dangerous "Split Bus/Rule of Six" panel (which, granted, can be solved by subpaneling if the service wires are in conduit).
- They don't have enough spaces, because the same genius who set it in concrete also picked a 16-space panel. "But it's 32 circuits!" which buys you nothing in NEC 2020.
Of course, that's what we know today about 1980's panels. What will we know tomorrow about today's panels? Will we find out that Square D HOM's relatively young plug-on neutral scheme is as dangerous as FPE/Zinsco? Will GE drop all support for older panels (again) just as JFCI breakers become mandatory? We don't know. That's the point.