Can it be done? Sure. Is it easy, is there instructions and will it work? No, depends and unknown.
If you're region swapping a firmware and have a hardmod (or if it's an EmuNAND in rxTools, maybe...) you can check the
region swapping thread for instructions that may work, but it's a long read.
If you just want to access another regions' shop without a region swap, then
- Region lock still applies, so any content downloaded won't work without further means to launch it.
- Theoretically, if you unlink your NNID and know what memory values to set, you can access any other regions' shop. However, this is untested if it actually works to purchase content and you can't download free content (updates) without a NNID, and trying to have one of a different region connected while doing so = ban.
- As far as I know, step 2) is basically undocumented, just testimony that it happened (not that the testimony is illegitimate, just that no instructions exist.)
In any case, it's fairly impractical as it stands unless you are region swapping, and have a hardmod if it's SysNAND. I believe there is still investigating going on, but so far this is as far as it's gone.