Except "batch on replacement" is ludicrously hard to do.  I called it super sending and spent like 6 months working on the (generalization of that) problem (fully decoupling "payments" from "bitcoin transactions" and handling inbound/outbound correctly) and I like to think I'm a decent programmer, but had to give up as I could never figure out how to handle get a handle on all the complexity (which really explodes when you consider reorgs, inbound payments being replaced etc.).

I actually think it's the hardest (pure) programming problem I've worked on, and don't feel like I'd even be able to do it given another 6 months. I've never done "logic programming" but I almost feel like something like that would be essential, where you sort of logically describe all the high level concepts and ask it to solve what you should do. As just trying to handle all the cases imperatively just seems impossible to not end up in an exploded spaghetti nightmare of a gazillion states.


[Bit off topic, just ranting here incase you have any insights]