Low Mintages Good Idea?

Depends a bit on the country, I think. Americans consider their coins as rare when about 1 million are struck. I have some Maltese coins where the highest minting year had 30.000 pieces minted and the total mintage was 4 or 5 years...

And then there's of course the very famous known coins like the 1933 British Penny, 1933 American Double Eagle and 1913 American nickel. For those you can better start saving as their price is also heavily inflated by the 'hype' around it.

I think kanga is also very right when it comes to survival rates. I do know that a lot of silver and gold coins in the US have been destroyed due to the Gold Reserve Act of 1934, which probably makes the US coins from before that year significantly much more harder to find. The same goes for Europe, where the Nazi's confiscated a lot of gold and silver from the countries and territories they occupied. The hard part is that, therefore, total surviving numbers for each coin and year (and mintmark, where applicable) are unknown. Of course, chances are that if year A had 1 million and year B (being A+1) had 5 million for the same coin in the same series, about 5 times as many from year B would have survived, so that is why mintage would be a guideline, not an absolute truth.

Nevertheless, I really like your idea. You'd probably end up with a small, but exquisite (and most likely expensive) collection of coins that, for at least one piece, make a lot of people jealous.

Or you could opt for ancients where its quite affordable to own a unique coin from 2000 odd years ago. I have a few and it's really not that big a deal.

I have owned coins where only one or two other examples are known to still exist (these are from the 17th century so few have survived). However they were not necessarily worth a fortune because the market for them is small.

Other coins exist in far greater numbers (several hundred) but because of their history or because they have a wide appeal they cost many times what a much rarer (in numbers) coin might fetch.

The key is knowing what is popular and rare.

Which is not to knock your idea. Certainly here in Britain condition is the primary driver for prices, so any 'antique' coin in top condition is likely to hold its value. Of course, such coins are already popular, so few bargains are to be had. But if you can find common coins in uncommonly good condition you can be lucky.

Modern coins? They are generally produced in the thousands if not millions and everyone wants (and can afford to wait) for the top grades. So while 'the best you can find' strategy is a good one, don't expect to make your fortune!

It's also important to remember that there are fashions in coin collecting as with anything else. A certain type becomes popular, people buy, prices stall and it becomes difficult to get back even what you've paid. Will colourised coins prove popular in 10, 20 years? Who knows? But generally coins that have been used as actual means to purchase things, particularly for those that remember using such things in their youth, retain a degree of popularity. Things that are just made as souvenirs? That's harder to tell. But just remember how popular Beanie babies once were ... now? Not so much.

Personally, I agree with kanga, buy coins for fun and the enjoyment of owning a piece of history, not for investment.

The Peter Rabbit is just hype and I reckon will drop like a stone over the forthcoming years.
I repeat again especially pre 20C mintage figures are not necessarily the nrs bearing the coins date.
When you consider retailers mark ups,auction buying and selling premiums even eBay&paypal costs.Investing in coins takes 2nd fiddle to the joy/hobby of collecting.