Tenkar's Tavern, Greyhawk Grognard, JoetheLawyer, Diversity & Dragons, Esper the Bard, as well as a few others (G2 and Eldrad Wolfsbane) have made videos answering that question. ChubbyFunster punted the question which is no fun. I run the same thing through my head every few months (usually if I took over TSR instead of WotC back in 2000 but whatever). I don't make videos so I figure I'll just post. Assuming I was given the whole thing and carte blanche to control the product line without interference here is what I'd do, at least to start with.
D&D 2025, Spin off into a separate company with pretty much all the current employees (I'd let the employees pick and among those that want to stay with my 6E project I'd interview them and decide for myself). D&D 2025 project would have a new name and would live or die on their own. If Hasbro wants a My LIttle Pony or GI Joe version of a Role Playing Game this is the group they'd go to. This one would be all rainbows and characters never die and all that. Beyond that they can do as they will and good luck. Maybe it'll sell well, maybe not. That won't be my problem at that point.
D&D 6E. I'd take the 2014 edition and remove the fiddly abilities every level (and the archetypes that go with them). Those are the things 'character builds' are made of and I don't want any part of builds. Instead I'd have a proficiency bonus equal to the PC level. Clerics would get a re-work of Cleric Domains from 3.5 so a DM could quickly build a pantheon and have each deity meaningfully different. Also any naval stuff from The Saltmarsh adventures would be migrated into this book.
Starter Set I'd cut down the rules to the first 3 levels and bundle with The Keep.
The Keep I'd bundle this with the Starter kit and also sell it solo. This is (B1) In Search of the Unknown and (B2) Keep on the Borderlands. I'd update those two modules a bit and use the Keep as a base of operations for both. I'd also include interior maps and urban encounter charts for the businesses in the keep. The idea is a new DM has players explore Caves of Chaos until the DM feels comfortable enough to stock the Caverns of Quasqueton on their own. By the time they are done with both they should need no further help. Also by adding interiors to the keep we can emphasis urban adventures in addition to wilderness and dungeons.
The Borderlands Use the wilderness map from the keep and drop the pyramid/Ziggaraut from B4 Lost City into the swamp to the Southeast, and the hill from B5 Horror on the Hill south of the River (with the keep replacing Guido's Fort which was never detailed). This is not really a a follow-up as PCs should be high enough level to move on by the time they're done with B1/B2 but now you've got a large sandbox a DM could use again and again for starting players.
Lost Mines of Icespire Peak This would be both Lost MInes of Phandelven and Dragons of Icespire Peak. Put together to create a sandbox with a lot of adventure options. Some of it would need to be reworked but the core is a decent adventure for low-level adventurers.
Other Adventures. I'm not gonna go over every module here. Just know I liked the way they bundled modules into a single book in Tales of the Yawning Portal but they made it too big and they don't need to be hardcover. Three modules, maybe four is fine. I'd update the older modules. Basic or AD&D doesn't matter they are all being converted to 6E. If at all possible keep the modules in roughly the same tier of play or unified by theme/enemy. So perhaps X1 Isle of Dread (3-7) could be mixed with (I1) Dwellers of the Forbidden City (4-7) and or (C1) Hidden Shrine of Tamoachan (5-7).
Campaign Worlds I'd keep the most popular (Greyhawk, Mistara, Ravenloft, Forgotten Realms, maybe Kara-Tur) and customize the rules and monster/class selection for each to make the game feel different in each setting. Every module we published would include a bit about where on each of those setting that module could be placed (I think Yawning Portal did that).
Some settings (Planescape, Spelljammer, Dark Sun, Gamma World) I'd have updated to 6E and then released into the wilds with some kind of Creative Commons that allows individuals or companies to make/sell any kind of support they want but sales of the setting are still mine.
Lastly I'd return to others to their creators with my blessings (Eberron, Dragonlance, others),
Monster Manual I'd divide this into two or three books, broken up by tier of adventure. I'd go 4E style and have multiple versions of each monster (Slinger Goblin, Scout Goblin, Shaman Goblin) so the DM has more to work with. I'd raid all the previous editions for content if necessary. I love monsters and might want a new edition every few years.
Dungeon Master's Guide I'd update the current 5E with the best stuff from every edition of DMG: 1E, 2E, 3E, 3.5E and 4E. If necessary split out the Magic Items stuff to be its own book.
VTT I would not create or sell a VTT but I'd have some products for the VTT. A map pack of interiors for important buildings in Waterdeep, or Neverwinter, or Baldur's Gate would be helpful to a GM running their own campaign. Do the same for other settings. Someone that doesn't care for a setting might still find a bunch of maps interesting the way the old Citybook was useful.
Dragon Magazine I believe having a single source of info creates a sense of community that the websites don't. No Dungeon magazine, I'd makes sure Dragon was full of short adventures and divide Deities & Demigods into pieces and have that as a regular column but specializing on the Cleric-side of things instead of statblocks for the Deities. Repeat what was in Deities & Demigods and gods in different campaign settings and religions from novels. Doesn't have to be monthly, could be bi-monthly as long as its loaded with stuff. Run a bunch of contests for best dungeons, best monster, and use that as a way to find who to hire and who to avoid as useless.
So that's the basics plan.
