You are trying to solve non-problems.
First, you speculate that the value of gold would collapse if a huge deposit was discovered on an asteroid. Just FYI, the cost of getting to an asteroid and bringing anything back would far exceeds the value of gold, so such a deposit would have basically zero effect on terrestrial prices. Plus, of course, such an idea is completely arbitrary and should therefore have no bearing on decisions here in the real world.
Gold skeptics often cite two issues: first, what would happen if the gold supply suddenly increased, and second, that there isn’t enough gold for it to work.
Man has been searching for gold deposits for ages. The odds of some large, new, undiscovered source are very, very small, and getting smaller every year. In fact, if anything, the reverse is more likely: existing gold supplies could easily not be renewable once they have been fully mined. Total annual gold production is about 1% of the existing supply, and it has been at around that level for quite some time. Also, keep in mind that bringing new gold to market requires effort: mines have to be located, then mining equipment has to be created, the mine itself has to be created, ore has to be dug out of the ground, then refined, etc. The people engaged in that work are, of course, entitled to compensation. The effect on the overall money supply would be relatively insignificant, particularly in light of increasing population.
Regarding not having enough gold: the misconception here is that gold would have to stay at its current value if it was used as money. The value of gold can be anything that people agree on. Because gold is nearly infinitely divisible, it turns out that any amount of gold is enough to run the global economy. It’s just that the less of it there is, the higher its value would be.
Regarding the idea of substituting some other commodity: an ideal money needs to be something that is easily recognized by most people as having value. Gold has been used as money for 5,000 years for a good reason. No other commodity can make that claim (although silver comes close). Also, for an ideal money, you want to choose something that can’t be created easily. If dolls were money, you can imagine how many doll factories would suddenly be created. The advantage of gold is that it’s hard to find and hard to bring to market: it’s self-limiting.