Hot take: I love this game, especially its soundtrack.
Combine Sonic the Hedgehog 4: Episode I, Sonic the Hedgehog 4: Episode Metal and Sonic the Hedgehog 4: Episode II altogether along with the cancelled Sonic the Hedgehog 4: Episode III and call it Sonic the Hedgehog 4 DX with the title screen being like Sonic Mania's title screen
Have it be more faithful the Mega Drive/Genesis games with better controls, elements from Sonic the Hedgehog 1, 2, 3 & Knuckles, Advance, Rush, Mania, Origins, Superstars, etc. with Wisps and more stuff
Replace the Sonic the Hedgehog 4 sound effects with the sound effects from the Sonic the Hedgehog games on the Sega Mega Drive/Genesis
Use Sonic the Hedgehog 4: Episode II's physics engine for Sonic the Hedgehog 4 DX, but fix the engine so that it resembles the Mega Drive/Genesis games more
Make the graphics be more like Sonic the Hedgehog 4: Episode II, but make them far more detailed with everything using cel-shading and colored outlines a la the Genesis games
Replace the Korg Triton (EP I/M/II)/Vacuum VST/Xpand!2(EP I/M/II) instruments with Yamaha DX7 instruments (example: Casino Street Zone (renamed Casino City Zone)'s brass synth getting replaced with Spring Stadium Zone's melody synth) with NO QUESTIONABLE INSTRUMENTATION CHOICES
Have a better Co-Op and VS. Mode, sound test, minigames, extras, etc.
Add settings such as Debug Mode (toggle on/off), a Game Style (options include Original which changes the game to the original Sonic the Hedgehog 4, DX which is Sonic the Hedgehog 4 DX, and 16-bit Mode which makes the game be exactly like the MD/Genesis games, complete with Yamaha YM2612+Texas Instruments SN76489 music and sound effects, with Classic Sonic, etc.), Character Layouts, etc. (a la Sonic 3 Complete), Music Percussion (Options: S1, S2, 3&K, Chaotix, 4A (Sonic the Hedgehog 4: Episode I), 4B (Sonic the Hedgehog 4: Episode Metal/Sonic the Hedgehog 4: Episode II), and 4DX which are the original samples of the drums used for the first two Sonic the Hedgehog games), Music Style (Original, DX, Blast Processing (which changes the music style to a music style that will satisfy the Sonic fans *if you know what I mean*), and Refresh which is Sonic the Hedgehog 4 2020 Edition's soundtrack) Super Cancel (toggle on and off), Space Harrier Mode, Fantasy Zone Mode, Sonic Ability (3&K, CD-93, CD-96, CD-2011, Mania, and 4DX), Graphics (Options: OG which is the original Sonic 4, DX which is Sonic 4DX, Old which is like the original Genesis games, and , which is detailed), Aspect Ratio (16:9, 21:9, 4:3 and 10:7), Audio Pitch (not just semitones), and Motion Blur (on/off)
Have better and smoother level design (especially in Lost Labyrinth Zone - Act 2 and especially Death Egg Mk.II Zone) and gameplay (and tone down the instant-death bottomless pits) as well as a better story and deeper lore
Have Be'en, Kalow, Mirage Island, etc. be CANON
Make Sonic go faster, add more momentum and add the Boost from the Sonic Advance trilogy
Have better running animations that resemble the MD/GEN games more
Add more characters including Big the Cat, Honey the Cat, Silver the Hedgehog, Chao, etc. and have it take place after Sonic 3 & Knuckles as well as adding more Easter eggs, adding costumes, skins, (e.g. Feels the Rabbit), and a couple of Sonic memes to be referenced
Add animated cutscenes as well as more in-game cutscenes
Improve the game's soundtrack by making it longer (just like the Bouncy Glow's Music Room/Jade Jovian extensions) and using game music-accurate MIDI/MID files as well as having the MacOS X/iOS/Android version using the iOS/beta version of Casino City Zone's second act's music and making the Switch version use MIDI/MID files like the Wii version of Sonic the Hedgehog 4: Episode I
Release it on November 24, 2026 on Nintendo Switch, Xbox One/Xbox Series S/Xbox Series X, PlayStation 4/5, PC, Mac OS X, iOS, Android, etc., commemorating Sonic the Hedgehog's 35th anniversary