react'ing to the need for a todo program

It is ironic that toy todo apps are a favorite way for programmers to learn a new toolkit, but I can't find the perfect real app, and may end up building it myself.  I've been daydreaming on the ideal app ever all the way back in 2005 (then I would have wanted it for the PalmPilot) and then 3 years ago I was taking a deep look at Apple Reminders as a possible substitute for AppiGo Todo, which I've been using pretty much since iPhones had apps. (I remember a big wall poster in the apple store showing the built-in notes app being used for a todo list, back before there was an app store or the default Reminders app - an odd reminder that the 2007 iPhone was a serious step down from the 1996 Palm in terms of being a PDA until Apple got its Appstore going.) 

AppiGo Todo is pretty good but gets several things wrong, and feels like abandonware. (At least the free version?) It has had a glaring bug in how it does attached notes for years, and I'm pretty sure they're they're never going to fix it.

In increasing order of importance, here's what I want in a Todo app but find hard to find, and would emphasize :

• Snooze Button - dated Todos would have a simple "kick this can down the road" button. (Gmail is introducing this feature for its core web-based app)
• Hot/Medium/Cold priority - it's a sad fact in life that there are worthy(ish) tasks  that I may or may not ever get around to, but I don't want to go away forever. A "Cold" priority, with appropriate filters so I'm usually not seeing them mixed in with the more pressing stuff, would be great. ("Hot/Cold Todo" is a possible name for this app if I ever make it) 
• One Big List showing multiple categories - many programs have categories or tags, and just about every single one I've found either says "here's every Todo with every tag all mixed up" or "here's a big list of categories, please navigate into each sublist separately if you want to see the corresponding tasks".  I long for a unified list of categories, but with headers acting as visual dividers - these headers would be customizable per person. For me, they would mostly focus on where I am where they need to get done (home, work, online, store) with some special topics (bands, projects). Each category header line would have its own "add task" button. Ideally each task in a category would be manually sortable. Also, whole categories could be collapsed when it's time to focus elsewhere. ("Buckets" or "Starbuckets" would be another possible name for the app, if I thought people would recognize those as corresponding to GTD/Getting Things Done Bucket system) 

Recurring Todos are table stakes (with a "set up next reminder based either on the date the task was first set, like for a recurring bill, or for when it was completed, like get a haircut X weeks after I got my last one.) Date-based recurring Todos are especially tricky - ideally you want to be able to say "the 3rd Thursday of the month" as well as "3 days before the end end of the month" (like for rent).

I would also avoid the biggest UX misthink I've seen in Todo apps featuring sorted/dated tasks, namely that the more a task is "overdue", the more urgent it must be, when usually the opposite is true (it has been demonstrated that the task can slide a few days without major consequence!)  I guess this would be less of a problem in Appigo Todo if it didn't make the other misthink of "any task with a date is more urgent than any task without a date, so we're going to put anything without a date waaaaaaay at the bottom". So my life with Appigo is a big list of 20-40 minor things, most of which are technically overdue but it doesn't matter, and I always have to scroll down to where the recent and daily things are scrolling up.

I'd also love to make a web interface to get to my data - with stuff like Simplenote I've seen how useful it is to be able to use a computer keyboard to supplement the device that's always on my person. (It might be interesting to have a second mode of bulk editing as text, where lists could be converted into and back from a text memo format, like

Some Category

-a task

-another task

Some Other Category

-yet another task

could go back and forth. That reminds me that it would be great to be able to make subtasks, and handle projects thats way, but that doesn't seem as crucial to me as it once did.)

I'm in training for React now, and I'd like to look into React Native for making an iOS client. Here's hoping! But if I get it done it could be a real gamechanger for me.

UPDATE: The app 2do may cover enough of those things - especially the "one big list" one - that I maybe should just switch to that. It doesn't cover everything perfectly (and of course covers lots of others people's preferences that I'd rather not mess with) but overall seems pretty great.