I never liked disc swapping for one, second some of those carts can cause a problem with the cart slot.
At least in the US, you wouldn't need anything besides the Saturn console itself. It works with all the US parts like the video out, controllers and power plug. Works fine on US power.
Another thing I found is that since I am not using a special cart to play JP games on US Saturn, I have nothing in the cart slot. So then you can buy JP Memory carts and be able to see and use those save games. The last thing I bought out of Japan was 3 memory carts and they all had various save data on them... Not that I have any of those games yet... I've specifically been buying the jank Saturn games, rather than the popular ones.
So for me, I'd much rather have the actual console to play a thing on if possible, so I don't have to bother with gimmicks. The Retron being the obvious detractor from that, to play Famicom games and of course it is just using emulation. I'm not adverse to using emulation even in a computer. Since to me it seems viable to be able to play Xbox or Japanese Playstation games when I get to those and do not yet have a workable console.
For EU console stuff, at least disc based things, I probably won't bother with PAL consoles due to the issues of power conversion and display compatibility. But most of my EU games are for PC or region free systems like Game Gear, SMS and Game Boy.
I have only 1 Japanese console, the Saturn, and I bought that from someone on a forum. Otherwise, you can easily find them on Ebay or YAJ, but shipping can be a little weird these days.
Is there any advantage to having a Japanese Saturn aside from the cool colors? I just use an Action Replay cart to play Japanese Saturn games, it's worked for everything I've tried but I have no idea if it's 100% compatible.