Line type scale - limitation

Is there any reason why there is a boundary of 100 units for line type scale? Shouldn’t it be limitless?

It’s a scale factor so isn’t 100x the scale adequate?
Your options are to link the linetype scale to the Layouts if that’s where you’re using them, or change the pattern definition since it is stored in the 3dm file.
It seems like this is a reasonable precaution for unintended consequences.

What problem would allowing a higher scale factor solve for you?

I would mainly like to display the line type (fe. dash dot) in the model display view. When working with larger models in milimitres template, even 100x is not enough to see the change. I wanted to avoid creating more line types, because I use the settings “match the line type pattern” when printing and I like having the same line appearance on the paper regardless the layout detail scale.

What would be those unintended consequences if the number was higher or just unlimited?

From my years on tech support, they are legion.
I think your best options are either toggling the Match pattern tools and you switch from modeling to printing tasks, or add the other linetype patterns and switch them.