@max: You wrote about need to compute possible angles and notify about them. It's already possible. Just tap on track on map and at bottom panel choose "Navigate". You should see screen called "Navigation generator", that allows you to generate navigation for whole track. So Locus will work as an "real" voice navigator.
@christian: no news here. To be true, I'm little bit lost in this topic. I tried to read it one, but same

So what is wrong and what is expected?
Just two notes
- turn on screen during guiding should work for notification "Too far from track", but also for a notify on next point. It won't work for you?
- power consumption - you wrote 60% more, but more compare to what? To situation without guiding? If Locus do not need GPS, for example for guiding, then GPS is turned off when you hide locus or turn off the screen. Because 'Guiding' needs GPS, it will consume quite a lot more power.