First off, this doesn't avoid the technical challenges present in the last suggestion: there's no denormalized "top answer score" column available, so calculating this would require querying all answers attached to each question across all sites. Oh, yeah - there's no denormalized "pending close votes" column either.

So this isn't really feasible. You can stop reading now, if you want - the rest of this answer just disputes the premise.

##Unintended consequences

I did a quick simulation of your criteria on a few sites (SO, SU, TWP and Progse) just to see if there'd be a dramatic difference in the results... There wasn't. More or less the same questions came back, in more or less the same order; a few questions gained or lost position further down the list, but the single most noticeable difference was that the "hotness score" for all questions suffered on the sites that weren't Stack Overflow. The most noticeable effect of implementing this would be an increase in questions from SO to the detriment of other sites; given we're already heavily penalizing SO questions in order to give other sites a chance, this would be a pretty counter-productive change.

###Answers as indicators of "hotness" vs. "hot answers"

You appear to be searching for a way of finding "hot" questions based on the presence of "hot" answers. (Aside: [there do exist lists of hot answers) This is an interesting idea, although if you check the 10K tools regularly you'll know that popular answers generally go hand-in-hand with popular questions so the outcome is unlikely to be dramatically different from what we have today - indeed, it might well just increase the number of problematic or "sticky" questions in the list.

Philosophically though, this isn't even particularly relevant. This isn't a list of answers; it's a list of questions. And answer score is a fairly narrow indication of the popularity of a question: they align cleanly when there's an awesome Eric Lippert metaphor to be had, but this just treats answers as a function of popularity, not as an independent indicator. Let's consider a few common classes of questions:

1. Bikeshed questions: Everyone has an opinion here, so a good many of them try to post it. Voting tends to follow the "find an opinion that matches your own and up-vote it" model. Let's face it: these questions should usually just be closed.

2. Hard, subtle or thought-provoking questions: Everyone has an answer here too, and most of them are demonstrably wrong. Answer scores vary wildly between top and average.

3. Trivial questions: There's one answer, and everyone knows it, so everyone posts it immediately. FGITW comes into play here, but if folks put a bit of effort into their answers it's possible to end up with something fairly similar to the bikeshed: everyone's just voting on their favorite way to present an answer.

Answers are an indication of popularity in all three cases. Penalizing "non-hot" answers can actually hit #2 the hardest. The trap you most want to avoid is the naive rewarding of questions that get the most "hot" answers, as this is a recipe for bikeshed promotion: the current system does this a good bit of the time, but your proposed changes actually make it worse by promotion questions that don't have wrong answers. Therefore, I would be opposed to this change even if it were technically feasible.

I sympathize with the folks participating on sites whose primary topic is seemingly filled with bikeshed questions, but them's the breaks: if your favorite topic has been driven off of several existing sites due to the problems it caused there, you have to kinda expect these problems when you sign up for a site dedicated to it.