I have a simple solution for Pascal muggers. I assume that, unless I have good and specific reason to believe otherwise, the probability of achieving an extreme utility u is bounded above by O(1/u). And therefore after some point, I can replace whatever extreme utility is quoted in an argument with a constant. Which might be arbitrarily close to 0.

In some contexts this is obvious. For example if someone offers you $1000 to build a fence in their yard, you might reasonably believe them. You might or might not choose to do it. If they offered you $10,000, that's suspiciously high for the job. You reasonably would worry that it is a lie, and might or might not choose the believable $1000 offer over it as having higher expected value. If you were offered $1,000,000 to build the same fence, you'd assume it was a lie and definitely wouldn't take the job.

By this reasoning, what should you think in the limit as the job stays finite, and the reward tends towards infinity? You hit that limit with the claim that for a finite amount of worship in your lifetime (and a modest tithe) you'll get an infinite reward in Heaven. This is my favorite argument against Pascal's wager.

But now let's bring it back to something more reasonable. Longtermism makes moral arguments in terms of improving the prospect of a distant future teaming with consciousness. But if you trot out the Doomsday argument, the a priori odds of this future are proportional to 1 / the amount of future consciousness. Given the many ways that humanity could go extinct, and the possibilities of future space, I don't have a strong opinion how to adjust that prior given current evidence. Therefore I treat this as a case where we hit the upper bound on the probability of the reward from the scenario is bounded above by a reasonably small constant.

My constant is small in this case because I also believe that large amounts of future consciousness go hand in hand with high likelihood of extreme misery from a Malthusian disaster scenario.

There are a couple of potential solutions here.

One solution is computational personhood.

The human mind contains about 10^12 or whatever bits. So there are at most 2^10^12 minds we would recognize as human. If you think that simulating the exact same mind 10 times is no better than simulating it once, and you deny the moral relevance of vast incomprehensible transhuman minds, then you have some finite bounds on your utility. Some finite set of things that might or might not be simulated. This lets you just deny that 3^^^^3 distinct humans exist in the platonic space of possible minds. 

The other solution is solomonov reality fluid. Reality has some magic reality fluid that determines how real something is. A bigger universe doesn't get more realness. It just spreads the same realness out more widely. 

When you see a quantum coin get tossed, you split into 2 versions, but each of those versions is half as real. This removes any incentive to delay pleasurable experiences until after you see a quantum coin flip. 

Ie otherwise, eating an icecream and then seeing 100 digits of quantum randomness would mean experiencing eating that icecream once, and seeing the randomness first would mean the universe being split into 10^100 versions of you, each of which enjoys their own ice cream. So unless you feel compelled to read pages of quantum random numbers before doing anything fun, you must be splitting up your realness between the quantum many worlds. 

If you don't split the realness in your probability distribution, you are constantly surprised how little quantum randomness you see. Ie suppose there is a 1 in 100 chance of me putting 50 digits of quantum randomness into this post. And you see I don't. 1%*10^50 =10^48, meaning your surprise, that I didn't add that randomness should be 1 in 10^48 if you consider all the worlds with different numbers equally real. 

Now probability distribution realness doesn't have to be the same as moral realness. There are consistent models of philosophy where these are different. But it actually works out fine if those are the same. 

So if we live in a universe with a vast number of people, that universe has to split it's realness among the people in it. Ie if there are 3^^3 people, most of them get < 1/3^^3 measure, making them almost entirely imaginary. 

If there is some entity that is taking some large number of people, and then selecting one of those people to decide the fate of all the rest, your prior that you-in-particular are the one that the entity selected should scale with the number of people in the group. If the group contains 3^^^3 people, you need enough evidence to overwhelm the 1/3^^^3 prior that you in particular have been singled out as special within that group.