A Preferable "Builder Verification" Alternative
I am strongly of the stance that Builder Verification is a bad call; a lot of players might be aces at building bases, but not-so-hot when they're raiding. If Builder Verification is implemented, such people will not be able to build to their maximum potential, and it will make the whole process of building much more tedious; having to replay your own bases repeatedly when you change things, or prestige, or whatever. It works in something like Mario Maker because you don't have to tweak or make your maps any more than you desire, but in Meet Your Maker you're required to re-make, prestige, and re-post your bases a minimum of 10 times for maximum effect, which will not translate to having to play your own base 10 times, but probably two, three, maybe even four or five times at least, per prestige, so even if you're only tweaking your bases a little bit you've got to clear it 30 times, per base, in a game where lots of people have dozens of bases; basically meaning a good chunk of your Saturday afternoon is going to be spent playing through your own bases some odd 700 times.
Instead, I propose a much more streamlined and easy-to-impingement alternative: Just display some statistic related to clearing the base on the Outpost's listing. Something like Average Deaths, Fastest Clear Time, Total Clears (per current prestige), or something like that. Any such metric would be more than enough for a player to eyeball an Outpost and surmise whether or not it suits their fancy. This, combined with the decision to remove the penalty for Abandoning an Outpost would be more than enough to leverage just a little more choice and overhead, so they can deduce if they think they're walking into a fun time, or a wall of Sentinels, and does nothing to make the building process slower or more tedious. Full-on brick walls of Kill Boxes will likely see a decrease in runs, Raiders won't have to hop into any bases just to get blindsided by mob walls, and the Builders can keep on building freely.
As for which metric exactly would be the best, I am not sure. If you wanted to just show 1, to still keep some mystery as to what to expect for people not buying their boosts, then that's okay, but you'd have to be very particular on what metric you showed. In this case, Average Clear Time would probably do the most to help with just a single metric, I think; but their could be a better one. If you're willing to show more than one, then really any two combined would be more than enough information to work with when choosing which Outpost to run next; not even necessarily taken from the ones I've listed here.You could, alternatively, show a generalized value for the average. Like "Kill Rate: Low," "Clear Rate: Stable," "Clear Time: High," or something. A vague, generalized heads-up of what sort of time to expect. Just one though.
TL;DR: Builder Verification/Validation/whatever = bad. Showing a metric that lets the players deduce whether or not they think they're walking into a bad time = good. Retains freedom and choice on both sides of pay, just giving the Raiders a little more info to work with to make more informed choices without ruining the mystery of what to expect out right.