Not related specifically to the linked game, but a general suggestion

I think the current leech system is flawed. I find the automatic leech option that is provided to be hard to use in a good way, and also risky to use as it is easy to forget updating it, and you could end up taking leech when you do not want it.

Example 1: I upgrade to a temple. Now my neighbour must accept leech before I get to select a favor tile and finish my turn. In asynch games this could take a long time if my neighbour is sleeping. Even worse, I might go to sleep before he accepts leech, and then the game waits for me to select favor tile and finish my turn. It cant take 10+hours just for my single turn to be completed. After all this, maybe I realized I wanted to upgrade to temple on another hex, and I undo my turn!!
Suggested solution: Let me select favor tile and finish my turn (including conversion of resources) before my neighbours have to accept/reject leech.

Example 2: I had a game where I was passing, and before passing i converted some power to coin since I had a lot of power income. However, I forgot to set the automatic power leech to 0, and after I passed another player built a lot of stuff next to me. I ended up accepting a lot of leech that I did not need. This cost me about 8 vp.
Suggested solution for this situation: Always reset the automatic leech to 0 at the start of a players turn, so that the worst case scenario is that things take a little more time, and not that you pay a lot of vp that you did not want to pay.

The reason for me that it is easy to forget updating leech setting is that they are "hidden" at the bottom of the screen. Maybe the leech settings could show up at the top of the screen when I am about to finish my turn (when the confirm-button appears). This way it is easier to remember setting up the auto-leech before finishing the turn.

Example 3: You might want to pay 3vp for 4 power exactly once, but no more times, as this would give you the resources you need for your plan. In this case you can not use the automatic leech option, since it would accept all leech you get until your next turn.
Suggested solution: Have a way to tell the game the maximum leech you want to take combined, in addition to the maximum vp you want to pay for a single leech. So max leech can be for example 6, and max vp payed for a single leech can be 3. Now, if you get a 4 for 3 you will accept it, but if you then get another one from the next player you will reject it since it would have given you a total of 8 leech when your total was set to 6.

So a lot of suggestions here I realize, but the general thing I want to say is that the leech system is flawed for asynch play. The current implementation of auto-leech is hard to use optimally, and easy to forget, so it is risky to use. This makes players not use it, and when players are not using it the games take a long time because often one player can not finish his turn before another player has accepted/rejected leech. I dont know the best solution for this, but there are a few suggestions above.

Oh, and another suggestion that I forgot about:
Have an option to automatically reject leech. Now, if I am offered more leech than I automatically accept, I still have to manually reject it. It would be nice to have an option to always reject leech.

Great suggestions, but your last one is already implemented. It's called "Automatically decline spending VP for power"

Oh, wait, you're saying auto-reject over the configured limit, not auto reject > 1. Got it.