Interesting project.

As for Task Warrior, I think you are over thinking your 2 main problems.

1. The jump from one evening to the next morning just reflects the day's expected progress. It would be clearer if you did the position calculation in days, which you can get by calculating the start, end and current days from the start, end and current times.

   If you want hourly resolution, multiply the difference in days, and the scheduled number of days by the number of working hours per day. then calculate the current working hour from the current time:

   $workHr = $currentHr - $startHr;
   $workHr = $maxWorkHr if $workHr > $maxWorkHr;
   [download]

   Either way, you get jumps. But by using days (or work hours), you get consistent jumps, reflecting the current day's (or hour's) goal.

2. This is really a matter of planning a reasonable set of subtasks for each task. As long as the tool (Task Warrior or yours or other tool) supports subtasks, you can work around it.

That said, your description of the second problem includes the solution for submitting a feature request: divide the feature in to sub features.

So, first submit a request for a feature to estimate task progress by the number of sub tasks completed. When that is completed, submit a new request to enhance the task completion estimate by summing the scheduled days for each completed subtask, then divide by the sum of the scheduled days for each subtask. After that, a request to enhance resolution from days to working hours.

Then you could consider a request to calculate the urgency of each task by comparing estimated progress to expected progress.

Each of the above 4 requests could be described in 2 sentences and 1 to 3 formulae. And as long as you submit the requests one at a time, they are (probably) not overwhelming.