A way to say where I 'need' to be for various times during a trip (pre-planned events, arrival/departure times + places, any business meetings), and then to have suggestions for things to do in the between-times and spaces.

In other words, it's a routing problem - I have these fixed points in space + time - what interesting things/events exist in-between those and are routable?

(also needs to allow sensible amounts of time for food breaks, lots of buffer time to enjoy the surroundings, etc)

This! It would be nice if the places recommended were aggregated from the typical go-tos for travel (Yelp, TripAdvisor) - rather than starting yet-another place for reviews/opinion content. Also potential integration or partnership with Rome2Rio and/or Uber transport suggestions.

Currently I am doing all this manually in various apps, and entering the data into TripIt (which is also sort of ugly).

Have you watched The Layover on the Travel Channel? Its format is similar to what you describe.

great idea. Do you want to be able to get public transit times and locations (bus stops etc) on a map?

How about adding all points of interest and having the system suggest the best way to plan for the day?

I've noticed that people travel very very differently. So I would enjoy a guide that segregates users into the different reasons/ways they travel. For example some people will go to a foreign city specifically to see any ancient sites, historical museums and to people watch. Someone else might go to the exact same city but would be more interested in the food and learning the language. Same thing with safety vs adventure. Most travel sites try to fit all of this into a single "guide" which means that the typical reader probably doesn't care about half of it. So an app that allows me to select a city and then filter it's suggestions on the type of things I want to do would be much more useful than just a single long article. Then once you have this data you could rank cities as the best for historical sites, romances, nightlife, food, etc.

I'm satisfied with the current quantity and quality of online travel guides.

I want something with printable "zines" with recommendations for places to eat, sleep, and visit.

Like this, but printable and free : http://www.telescopecards.com/

I like to travel without my "devices" - I DO NOT want something that relies on my cell phone or cell service to work.

For me personally, safe places to go and clean places to go and eat. You could say that I am more about the comfort rather than the adventure. Tips and tricks on how to use public transit without getting me into trouble would be good. I am also big on food and would love to hit the finest restaurants (budget and cleanliness in check).

so points of interest plus nearby attractions and places to eat all in one page?

I believe most guides/sites already the general points of interest and nearby attractions. The issue for me with those is that it's not entirely personalized to my needs and taste (comfort, luxury and convenience).

I know friends who are into street food, living in hostels and being fully immersed in the culture. For myself, I prefer living in more comfortable hotels and eating at restaurants. Seems like the guides out there are either very generic or catered to my friends who are more adventurous. But nothing for the slightly conservative, affordable luxury traveller.

I would like to be able to build schedules. Not necessarily for a specific day (though that as well), but just "day plans". These should then of course have a corresponding map, as well as estimated distance between places with various forms of transit.

It's difficult to find a tour guide (professional) when you are an independant traveler. You are just acces to buy some activity but not to find a proper tour guide for a city or a monument.

Videos of just walking the streets of various cities. It's nice to have pictures and descriptions of the usual go-to places, but show me what the place is actually like.

do you mean sort of like google map but professionally done?

How long do you think the video should be? and from what vantage point? maybe filmed by a drone? or on a bike?

Also do you want videos from the insides as well?

Just walking videos going down the street, maybe showing the architecture, the stores, the people. You get to hear the sounds, see the sights, and get a sense for what the pace is. It could have narrative or not. It could be indoors or not. I think this is something that can be crowdsourced.

I am currently watching a series on Netflix called "The Layover" by Anthony Bourdain. It's a great travel show, but I wish it would show more of the street life of the places he visits.

Have you used tripwolf? It covers everything that I'm aware of wanting

I think tripwolf has a lot of great info and features but the presentation is not really great.

Updated cost estimation of the attractions, restaurants and transportation.