Surely time units should have very little variance between soldiers (we all share the same time) but be impacted upon depending upon the other statistics.
What I mean is that, for example - weight currently carried should reduce time units modified by the strength value. If a character has better accuracy or reactions then they should get less of a TU penalty for doing those actions (reaction shot / aim)
I understand that the way the system works, if you exceed weight then you suffer penalties but what this means (I believe) is that a soldier carry nothing can move exactly as far as one carrying all their kit but below they weight threshold.
Soldiers could dump all their kit bar the med kit in order to cross a distance and treat an injured soldier.
TU's are more level in this way but skills remain more varied then I believe it would be easier to keep soldiers skills more distinct further into the game rather than ending up with soldiers super levelled out and equal in ability.