This is not possible. I mean it is, and it isn't. What the SNES uses is VERY specific to it especially in battles. If the sprites get any larger, it will eat other sprites on screen and cause some HORRENDOUS lag.[...]
He was originally talking about porting SNES graphics to GBA, not the other way around. Anyway, GBA version has too many issues, and basically hacking it to fix the game would be close to an entiere rewrite of the game.
I don't know if any of the time warp effects are possible to fix via hacking, but I suppose it's interesting to know some of the assets are still contained in the rom somewhere...
Of course this is possible, but why bother if the GBA version is bad anyway ?
Also I quickly looked at the scene, apparently the background scaling is not done with IRQ as I suspected, but with the DMA0 channel. So in order to fix the issue, one should compare how the channel is used on both versions of the game (working (J) version and broken (E) version), and see what differs. A random guess could be that the size of DMA transfer is wrong, for example half of the original size, so that could explain that the scaling effect "advances" twice as slow as it's supposed to. However, if that was the case, odd-numbered scanlines should show glitches, which they don't, so I don't have a full explaination. Another possibility would be that the DMA itself is correctly set-up, but that the routine preparing the scroll/scaling data is messed up and updates wrong values to RAM.
On top of that the SNES version is very hard to go back and play these days, with its antiquated battle system.
On my side I grew up with the SNES version and only played the other versions dozen of minutes for a try, and I see the battle system as "normal". I haven't played any other Tales of games either, so SNES Tales of Phantasia is the only game in the series I've played a lot. I don't find it "hard to play". However, as much as I love the game the only real issue I have with the game is how labyrinthesque the dungeons are. I doubt the other versions of the game are any different, but maybe you can inform me on this point ?
Maybe a port of SNES music to PS1 version would be the most adequate, as this would allow other popular ehancements to be played alongside the original music. The PS1 music really sound cheap-ass to me - despite the system allowing technically supperior sound to SNES. However this wouldn't solve the portability issue.
So maybe a hack improving the SNES version and a proper translation would be the definite answer, as Heaven Piercing Man said.