The proposal will have a broader research space of contribution. But should include well-defined boundaries - what is in, what is out - of the research space. Getting this "right" (size and shape) for a PhD is key.
The opening should setup the problem statement. Motivate the area, describe state of the art, indicate what is not done. This leads the problem statement. It doesn't have to be monolithic - there could be sub-problems in it.
Then, come up with research aims. These are objective "chucks" of research (think of a research paper, if that helps) that all together, will address the problem.
e.g.,
Aim 1: Model target selection time using an existing dataset.
Aim 2: Assess how user accuracy varies with latency in a shooter game.
Aim 3: ...
The proposal will then have a series of methodologies towards addressing each aim. There might be tasks for each methodology that can be worked toward and check off. This makes the work "concrete" and allows for planning.
Provide information, preferably visible (e.g., color-coded table, maybe with three levels) showing progress towards the tasks and aims.
Produce a timeline as to when tasks/aims will be done.