Does anyone know of mods that force you to transform to a werewolf at certain times? Because in Requiem you get +100HP and stamina even while not in beast form if you are a werewolf, and I think this could be a more interesting way to nerf that.

I know that moonlight tales forces you to transform at a certain time of the month, but that seems like it could be just annoying (waiting 48 hours outside of whiterun so people don't hate you eternally once you transform). I'm thinking more along the lines of during combat, if this or that happens you will transform, and maybe you can't transform manually. You should get massive damage reduction during the transformation though, since it will kill you every time if you don't.

If there aren't any mods for this, are there any good self-imposed rules you can think of that do the same thing? I.e. "whenever you run out of stamina you must transform" or "if you get hit by two arrows in the same fight" or something? And how would I give myself the damage reduction?

The forced transformations that MT offers are based on moon phases, and the exact chance that you will transform can be specifically set in the MCM menu. So you can have it that you WILL transform during a full moon, but you can also set it so that there is a chance to transform on every other phase as well. Plus, it isn't an instant thing, as you are given quite a bit of time to get somewhere out of sight, although this can be tweaked as well. I had two instances with a character where the transformations happened during the Dragonborn DLC(arriving on the boat), both at the start, and just before the last quest(i.e still standing in the Skaal village). Also, this happened a few times otherwise, like just as I was about to reach the top step before entering Markarth, and another while I was in the middle of Whiterun. Also, the waiting can be tweaked, but by default it is only a few hours(i.e 12 am to about 5 pm).

I'm not sure about the Damage reduction, but between MT and Bloodmoon Rising, it allows for the WW form to take on Dragons, although I'd imagine that with mods to make the game more difficult, it will still be a challenge, even if you aren't the glass tank the vanilla WW form offers. Bloodmoon Rising does give some bonuses to a WW character in human form, so it might be that this is enough to tank the damage while transforming, I'm not sure. I rarely chose to transform during a fight.