Instead of them just being a cheaty, one-time-use bonus, now they can be an actual strategic investment.
Each Insta Monkey in the screen will now display a price, and if you have that much money, you can spend it to place down the insta without removing it from your collection. The price is based on the total cost of the tower, and it upgrades, with a 5% discount per tier. (i.e. Tier 0s have no discount, Tier 1s have 5% ... Tier 5s have 25%).
In each game, you can use each of your insta monkeys in this way the same number of times as you have them in your collection. Also, for convenience, you can Right Click on a normal tower purchase button, and it will take you right to the Insta monkey screen for that tower.
With this mod, there's a new layer of decision-making involved about whether you're safe enough to save up for a discounted Insta, or you need the immediate value of placing and upgrading a tower normally.