Hello Peter,
If Studio One doesn't allow some time signatures that you require for your work you should search the feature request board to see if that Feature Request already exists, and if so, vote it up, and if not, create it. Studio One 3 Feature Requests The developers do pay attention to that board and the most highly voted requests there from users.
As relates to some audio loops in 7/8 or similar not stretching correctly, if you can demonstrate that in a short video or animated gif, you should do that and attach it to a support ticket so that a support rep can see it and determine how to proceed.