I think it would be nice to have the possibility to decide a fixed Text and Dimension (inclusive Arrows) height what is not affected by the Print scale. That means: If I have a given height of 3,5mm it will always be printed with 3,5mm - no matter what the scale for the printing is.
Yes, I see also the problem that I could run in space problems after I twitch to the Print preview - but that will also happen when I change the Text hight in the preferences for a 5:1 printing.
Maybe this Feature Request doesn't looks important if you are usually working with Metric Units but if you have to handle Imperial Units then it is a pain in the back to make always the calculation to get the same heights.
Try it by your self; 3,5mm = 0.137795" = 1":1"
Now I like to print it in 1":256" ops - to small - ok 1":64" ... no, to big, maybe 1":128" .......and QCad can't remember the previously numbers. ;-)