"Battle Pass" immediately gets a lot of scrutiny because of all the examples of awful, predatory ones like Fortnite's or whatever, which makes it difficult to discuss. Still, I think it's worth talking about for this game, because I do think it can work.
First off, one main concern I can immediately get out of the way are microtransactions. Spinker has gone on record to say that there will be no microtransactions (#╭🌵⬩ffw-chat message), so if a battle pass is implemented, everyone can be rest assured there won't be any.
Deep Rock Galactic has the perfect example of a good battle pass that addresses every concern.
- No microtransactions. You earn xp to level up for rewards, and you can gain tokens to spend in a tech tree for more cosmetics. It's all completely free.
- Seasons last ages, sometimes as long as half a year, allowing plenty of time for players to finish the pass before it ends.
- Even if it does end and you haven't completed any, you can always go back to old seasons to make progress.
- Before the ability to do old seasons was added, cosmetics you missed would be added to loot crates you can randomly find during missions. Every cosmetic is always obtainable for free in some way.
- These directly prevent FOMO
- Seasons come with brand new mission types and side objectives to do that relate to the season's theme, giving more variety to the game. Said missions and objectives always have a chance to appear in the mission selection regardless of the season. It gives devs an excuse to add more content, basically.
The game is already directly inspired by DRG. Far Far West can easily make one of the best battle passes ever if the developers keep taking what works from that game.