a starting ML of 70+ is not that uncommon with option points - so an arbitrary limitation of 70 gives most martial types the same ML, which is boring for me.
Yeah. Given a high SB a warrior character has a variety of weapon choices. Axes SB3, Swords SB4, Maces SB5 - plus option point. I'd hate to see a player choosing a weapon based on the ML70 limit.
I pretty much assume that a character with melee ML>70 has some sort of battle experience rather than the other way around.
I have had warriors in my campaign, but none of them have had extreme SB so their MLs only landed on 70-80 in spears or so which is fine by me (60-70 in the other weapon skills). So if I tell them that they can't increase spears more, it is fine by them, they increase another weapon skill (that is below 70), or initiative, dodge or better their other skills which are by far more difficult to increase than weapon skills.
The only time I have had characters with extreme attributes, they have been craftsmen.
Although I have had thoughts trying the 60 DRs method instead of the 5 OPs, then the players could do what they want.
Edit: I have (a bunch of years back) used the truncation method and it does the job well.