The BT wasn't in G/S. Only in C. Besides, the Battle Frontier has a WIDE variety of activities that I much enjoyed in Emerald. The Battle Tower is a classic, obviously, ever SINCE Crystal. It should still be in there.
HM's: 1.Cut, 2.Fly, 3.Surf, 4.Strength, 5.Flash, 6.Rock Smash, 7.Waterfall, 8.Whirlpool.
After you beat Sudowoodo, that fat guy should automatically come up to you and give you Rock Smash HM. Rather than it being a TM [one use only] that was used so commonly in the game, it really should therefore be an HM. Also, you had to talk to him manually to get Rock Smash in the first place.
I think think, overall, that there should be all 4 generation pokemon [when you obtained the National Dex] and no new pokemon/moves so you can trade back and forth between FR/LG/Ru/Sa/E [first 3 generation pokemon without 4th gen moves, like they required you to do when you traded from GSC to RBY], and obviously DP with any pokemon that knows any move.
Uhm, the Celadon Game Corner basment should be accessible, as well as the Underground Pass. Victory Road should be longer and have trainers. But I think there should only be 2 Victory Roads yet all 4 regions. The strongest gym leader should go up to like level 80. The E4 should go up to level 100. The movesets shouldn't be cheap moves that the pokemon learn while growing up, and the occasional TM's such as Fire Blast or whatever. Seriously good movesets for that pokemon should be against you to challenge you a little. It's fun for people like me who can only enjoy in-game battles =[
And for once, can you ACTUALLY BECOME THE CHAMPION OF THE E4??
I mean, the E4 people challenge you like you're not the champion; can't they say something like "Oh, champion. You've come to test to see if I'm ready? Very well, let's battle!" and when they win they should be like "HAH, now I should be champion" and when they lose they should be like "Well, not like I didn't expect that to happen..."
yeah... I'm sick of being crowned champion but not actually BEING champion.
Avatar: In memory of ieatwyverns <3
Thank you, Vasco <3