When creating a master slide, I think it would be very useful to be able to also modify the slide layout.
My understanding is that LibreOffice handles layouts internally and can not be modified. Because of this you may end up with your Master Slide design not being compatible with how impress then locates the objects of its layouts.
It seems that the layout have two type of components, a title object, and a content object. The different layouts are a combination of 0 or 1 title objects and 0, 1, 2, 3, 4 or 6 content objects. If there is a content object the style will also include a title object.
This is probably a pretty good set of default layouts - and it is probably not easy to generalize it to be user modified. But perhaps the title placement and size and the area used where the content objects are placed into could be modifiable on the master page? Then the Title placement as well as content boxes could be fitted into whatever graphics and footer placement is made on that particular master slide?
Just an idea that maybe can be discussed?
It appears to me that when importing a templates from MS PPT, the PPT title object is not identified as the title object and placement to use for the master slide. Another problem appears to be that the area used for placing impress’s content objects seem to be “any area where PPT has not put any objects” which often results in the content objects ending up in a narrow slice at the bottom of the page, or only using a portion of the total available space on the slide.
Not sure if my experience is unique or shared by the majority of users.