Generally I see Acts as a good idea to direct players towards parts of the game no longer in use, levels, warframes, weapons, you could even have an Act to do a quest (if it's repeatable), opens interesting paths. But that said, in current state the acts have some annoying parts. I've decided to put all stuff here:
1. Acts conditions
Why not do Acts with multiple conditions, like: "do 60 minutes survival in one go or 120/180 minutes total", players who want challenge - got it, players who do not want challenge or are learning or can't do challenge - got it. I am rather veteran player but I like to play for fun (and still gain the items), rather than a chore (and had to do Kuva Survival twice - certainly NOT nice doing it for 2h)
Would be even better if rewards (not Nightwave points but resources, credits, focus, etc) finally scale better with time ... one day maybe
I think Nightwave levels should NOT give Wolfcreds rewards (or whatever it will be called) - those should be given AUTOMATICALLY with each level (ie. 20 per level), this way any progress will reward players with possibly purchases, not just every 4 or so levels. And you open yourself to put something extra there as well
3. Acts completion required
For a system that was supposed to replace alert to require less player attention, it doesn't do the justice. I do so far average 4 ranks per week, on 10-week length I am required to do 3 ranks per week to complete the events, while it doesn't put pressure to play alerts as they come, it puts pressure to play to complete acts, some of them rather difficult, especially to new players (ie. new Switch players might not be strong enough to pass through them so easily). This looks like 75% of all acts are required to complete (considering points - missing any elite one hurts more).
4. Episode specific items
All the Wolf of the Saturn 6 items - what happens to them, I can understand cosmetics to be exclusive, but what about mods or weapons. Those should NOT be exclusive (I think you repeated so many times in the past "no" to exclusive weapons), does it mean it will come back as episode-2-WolfCred purchase or elsewhere?