It's doable. There are translated patches around (look them up on Shining Force Central), you can burn your patched Saturn disc to an ISO and mount it using an emulator, or burn it to a CD-R and use the disc swapping trick on a model 1 Saturn. If you have a modded Saturn, most likely a model 2 if that's the case, you just put the patched disc in, probably the most ideal case but I don't have a modded Saturn myself...
For myself, I played my Japanese Scenario 2 using a printed transcript, haha. Pain in the ass to say the least, but I did beat it. I then tried the disc swapping trick for Scenario 3, and it worked decently, but at some point I started getting disc read errors.
I didn't want to continue on emulators because I had transferred my saves from scenario 1 and 2, and didn't want to lose them, but I never finished scenario 3 so it's not much better. I might just restart the whole trilogy on emulator one day and save me the headache. I'd recommend you do that if you're ok playing with emulators.
And yes, those games absolutely rule. I would kill for a fully localized HD remake/port of the trilogy on Steam. Come on, Sega, pleaaaaaase?