Early access is usually great for multiplayer games. For single player, story driven games, early access serves as a way to spoil the game for customers who intend to buy at release.
ye but for sandbox games I feel like its pretty important because the scope of them is far too broad (especially if you add in all the platforms and languages).
Maybe save the main questline as the first major piece of DLC to avoid that problem?
Note that Larian's been doing it for Original Sin and Baldur's Gate. It seems to have worked out ok for them so far.
All software is early access in my opinion. Time to embrace that rather than run away.