Implementation of this feature wouldn't require much in terms of processing power or storage. It would just be a more interesting and engaging way of getting to pokemon beyond the current "click it on an overhead". Game programmers and designers could definitely work with this description to make a feature.
Sure. But it's not fun. Which is way more important than any of the things you mentioned. The first thing a game designer thinks of is fun, not system limitations.
What's not fun is the presently 'mapless' version of Pokemon GO we all have access to.
Sure I can see if I am near a Pokemon, but I can't actually go after most of them due to GPS jitter and the time it takes to walk/cross at lights in cities.
If I absolutely knew which direction to go there is a CHANCE I could get to a Pokemon before it despawns.
As things stand now I pretty much have to win a small lottery to capture one where I happen to be taking a scenic walk.
