I think you are over-thinking this. Its best to keep things as simple as possible. If you start introducing a track departure for one runway then headings for others, things will eventually go wrong. That's just the way things are.
How long are your aircraft from these runways going to be on these headings? One minute? Maybe two? They will need to turn on course and will likely do this after noise abatement (if you have that) at perhaps 3000 feet, yes? There may be different wind speeds and strengths but even if you have aircraft side by side from three runways they will all be affected by the wind in a similar way. Smaller aircraft will drift more and this will need to be taken into account.
We are trained professionals and should be able to foresee these variables and maintain a safe operation. Sometimes it is better to let controllers decide what is necessary to ensure separation at a particular time rather than have every eventuality covered by a rule in black and white.