So yeah, is there anything you'd have done differently with this game?
I would've done a lot of things, mainly in regard to regional design and Pokemon distribution, because both are just plain terrible in this game. Here's a few of the major things I would've done:
-Make Black City/White Forest, Rt. 15, and Marvellous Bridge available after walking to them from Rt. 14. Black Skyscraper/White Treehollow and the Poketransfer Lab would be closed until post game. The Lunar Wing would also be unobtainable until post game to prevent you from getting Cresselia until then.
-Add Rt. 10, Challenger's Cave and Old Victory Road back in as post game areas. After beating the game, you can first head north from Opelucid to Rt. 10 (Old Victory Road would be closed off until you come the other way). From there, you can cross the river and then go west to access Challenger's Cave from a new entrance, while the old one is blocked by a one way ledge. Meanwhile, you can proceed to Old Victory Road and must go through it to reach N's Castle instead of through New Victory Road (let's face it, that makes no sense that the Castle is suddenly a few miles east of the Pokemon League when it was directly underneath before)
-Pokemon distribution:
-Yanma- various Shaking Spots: Castelia Park, Lostlorn Forest, Rt. 12, Abundant Shrine, Rt. 22
-Remoraid- various Surfing Spots: Rt. 20, Virbank City, Virbank Complex, Rt. 4, Driftveil City, Rt. 6, etc.
-Blitzle- Virbank Complex, Rt. 16
-Corphish- Virbank City Surfing, Virbank Complex Surfing, Seaside Cave 1F Walking
-Crawdaunt- Seaside Cave 1F Spots
-Gligar- Rt. 4, Desert Resort, Reversal Mountain, Rt. 15, Rt. 11, Rt. 23
-Jigglypuff- Rt. 16, Rt. 14, Giant Chasm
-Clefairy- Rt. 16, Giant Chasm
-Lickitung- Rt. 16, Giant Chasm
-Ditto- Rt. 16, Strange House
-Slakoth- Lostlorn Forest
-Munna- Lostlorn Forest, Strange House
-Vigoroth- Abundant Shrine
-Wingull- Virbank City Surfing, Virbank Complex Surfing, Driftveil Drawbridge, Driftveil City Surfing
-Pelipper- Marvellous Bridge, Virbank City Surfing Spots, Virbank Complex Surfing Spots, Driftveil City Surfing Spots, Undella Town Surfing, Undella Bay Surfing, Rt. 13 Surfing, Humilau City Surfing, Rt. 21 Surfing
-Golett- Relic Castle B5F
-Bronzor- Relic Castle B5F, Celestial Tower 2F & 3F
-Bronzong- Celestial Tower 4F & 5F, Abundant Shrine, Victory Road 1F
-Beldum- Chargestone Cave B2F Spots
-Shuppet- Celestial Tower
-Heatmor- Reversal Mountain Outside, Victory Road Cliffside
-Durant- Reversal Mountain Inside, Victory Road Inside
-Carnivine- Rt. 14
-Larvitar- Rt. 15, Rt. 11
-Pupitar- Victory Road Inside
-Vullaby/Rufflet- Rt. 15, Rt. 11, Victory Road Outside, Victory Road Cliffside
-Mandibuzz/Braviary- Rt. 4 Encounter, Victory Road Outside Shaking Spot, Victory Road Cliffside Shaking Spot
-Sawk/Throh- Rt. 15, Rt. 23, Victory Road Cliffside
-Tropius- Rt. 13, Rt. 22
-Shuckle- Rt. 13, Seaside Cave B2F
-Magmar/Electabuzz- Rt. 9
-Palpitoad- Rt. 22
-Croagunk- Rt. 22
-Stunfisk- Rt. 22 Surfing
-Cryogonal- Giant Chasm
-Lampent- Victory Road 1F
-New Pokemon available post game
-Cascoon/Silcoon (both would be available, but one would be more common then the other depending on your version)- Pinwheel Forest Inside
-Scyther- Pinwheel Forest Inside, Rt. 18
-Machoke- Pinwheel Forest Outside
-Nincada- Pinwheel Forest Outside
-Pikachu- Rt. 3
-Pidgeotto- Rt. 1-3
-Staravia- Rt. 1-3
-Tauros- Rt. 3, Rt. 10
-Miltank- Rt. 3, Rt. 10
-Loudred- Wellspring Cave, Challenger's Cave
-Chimecho- Dreamyard
-Kadabra- Dreamyard
-Kirlia- Dreamyard
-Tentacruel- Rt. 17 Surfing, Rt. 18 Surfing, P2 Laboratory Surfing
-Arbok- Rt. 18, Rt. 10
-Electrode- P2 Laboratory
-Porygon- P2 Laboratory Shaking Spot
-Rhydon- Clay Tunnel, Challenger's Cave
-Graveler- Clay Tunnel, Challenger's Cave
-Dugtrio- Clay Tunnel, Challenger's Cave
-Unown- Underground Ruins
-Snorunt- Twist Mountain
-Shelgon- Dragonspiral Tower, Old Victory Road Outside
-Masquerain- Moor of Icirrus
-Gloom- Rt. 10
-Weepinbell- Rt. 10
-Sableye- Challenger's Cave
-Mawile- Challenger's Cave
-Stantler- Nature Preserve
-Parasect- Nature Preserve
-Breloom- Nature Preserve
-You can pick between Archen/Tirtouga in Driftveil City
-Move the Daycare to Flocessy Ranch
-Include the Vs. Seeker
-Bring back the ability to have your lead Pokemon follow you around.
-Elite 4's team is rehauled to include past gen Pokemon added to the Unova Dex:
-Shauntal:
Banette Lv. 55
Cofagrigus Lv. 55
Drifblim Lv. 56
Golurk Lv. 56
Chandelure Lv. 58
-Grimsley:
Absol Lv. 55
Crawdaunt Lv. 55
Scrafty Lv. 56
Bisharp Lv. 56
Krookodile Lv. 58
-Caitlin:
Sigilyph Lv. 55
Espeon Lv. 55
Gothitelle Lv. 56
Reuniclus Lv. 56
Metagross Lv. 58
-Marshal:
Throh Lv. 55
Sawk Lv. 55
Heracross Lv. 56
Lucario Lv. 56
Conkeldurr Lv. 58
-Minor tweaks to Gym Leader rosters:
-Burgh:
Yanma Lv. 22
Dwebble Lv. 22
Leavanny Lv. 24
-Skyla:
Skarmory Lv. 37
Swanna Lv. 38
Drifblim Lv. 38
Unfezant Lv. 40
-Drayden
Druddigon Lv. 47
Flygon Lv. 48
Altaria Lv. 48
Haxorus Lv. 50
-Marlon
Carracosta Lv. 50
Mantine Lv. 50
Waillord Lv. 51
Jellicent Lv. 52