That's still not a remake. Those advancements were made for WKC2.
A change in battle system and level adjustments is not a remake. So 'per se' or not...it's not a remake.
WKC2 will have a higher level cap, a higher rebirth level, a higher max GR, new quests, a change of drop rates, and all that jazz.
The only adjustments to WKC is, like Cyprus said, a clean up of graphics.
Playing WKC now will not change how you play it if you change over to the WKC2 disk. Changing the whole gameplay of the first one wouldn't make sense.
And I doubt BSC can only be S-ranked with the side-quest because the side-quest makes Big Red (the boss) weaker so he's easier to beat. Plus, that quest is only really used for quick GP because of how fast you can get to the boss battle. It will still be the best choice for GP grinding since you can get to BR and beat him at around five minutes (less if you have a good party).