I’m not an RPG gamer, I only checked out Witcher 3 because it reminded me of Red Dead Redemption due to the open world and horseback travel. Once I started playing I was hooked, within weeks I beat the main game and both expansions, then had another go because there were so many mission and story possibilities.
The game already has so much, but seeing as there won’t be another Witcher game for several years (if at all), I’m hoping CD Projekt Red could throw us fans a bone and add an endless mode to the game.
Contracts for creatures would keep popping up on notice boards (seen above), bandits and monsters would keep reclaiming villages and settlements, and new loot would appear throughout the land. I know it’s reducing Geralt to being a sheriff of sorts, but it’s better than nothing.
The addition of more random dialogue for Geralt would also be welcome. Hearing him say “Winds howling,” hundreds of times is really my only complaint with the game.
This mode would kick in once the main story and side missions are completed. Perhaps other Witchers like Eskel and Lambert could be unlocked and playable to spice things up in endless mode.
My one big request: allowing players to restore Kaer Morhen to its former glory and customizing it like Corvo Bianco in Toussaint (from Blood and Wine). The costs for this renovation would warrant a lot of grinding, so it would compliment an endless mode nicely.
This game is already huge, I personally feel that Blood and Wine is practically Witcher 4 (it’s that big), so I’ve no business asking for more. However it was so good that many games I’ve tried since have been underwhelming, so any excuse to go back to Nilfgaard would be welcome.
Dave's Geeky Ideas 
That sounds great to me!