Could you possibly take your prolific imagination for how this is misspecified or wrong, and turn to imagining ways to improve it or patch it up?
For example, suppose that winning A, instead of guarantees extending into the far future, merely gives you a very large gift in the near future.
Alternatively, suppose that all of your questions regarding A were answered "Yes".
Alternatively, is it not possible to price a bet offered to you even if you are uncertain regarding exactly how much you would win, if you did win?
Well, I'm not sure what it's supposed to specify.
For instance, under your first suggestion - that A is an immediate prize of e.g. money - the PLP becomes simple risk aversion of death vs. money. The original description seemed to suggest more than that, what with choosing whole alternative futures.
... Oh, no! I've been shot!
— C3PO
A strange sort of paralysis can occur when risk-averse people (like me) decide that we're going to play it safe. We imagine the worst thing that could happen if we go ahead with our slightly risky plan, and this stops us from carrying it out.
One possible way of overcoming such paralysis is to remind yourself just how much danger you're actually in.
Humanity could be mutilated by nuclear war, biotechnology disasters, societal meltdown, environmental collapse, oppressive governments, disagreeable AI, or other horrors. On an individual level, anybody's life could turn sour for more mundane reasons, from disease to bereavement to divorce to unemployment to depression. The terrifying scenarios depend on your values, and differ from person to person. Those here who hope to live forever may die of old age, and then cryonics turns out not to work.
There must be some number X which is the probability of Really Bad Things happening to you. X is probably not a tiny figure, but instead significantly above zero, which encourages you to go ahead with whatever slightly risky plan you were contemplating, as long as it only nudges X upwards a little.
Admittedly, this tactic seems like a cheap hack that relies on an error in human reasoning - is nudging your danger level from .2 to .201 actually more acceptable than nudging it from 0 to .001? Perhaps not. Needless to say, a real rationalist ought to ignore all this and take the action with the highest expected value.