Can a mansard roof / tent roof expansion be carried out with usable floor space?

hello since my previous planning so far provides for a house with a hip roof or pyramid roof I need additional space for storage, hobby room, office, technical room besides my living area. However, since I cannot achieve this with my ideas in a two-story house, I initially tended to build a basement. The previous offers with a basement do not quite fit my budget. After longer considerations, I came up with the idea whether it would be possible to convert and make the roof usable accordingly? The development plan stipulates the following rules: Max. wall height from top edge of the floor slab: 6.0m Max. ridge height 8.5m Roof pitch: for wall height 4.5 to 6m 15-25 degrees Would it be possible and sensible according to the specifications to expand the roof as usable space, maybe the technical room could also be in the roof Thanks

For 2 floors with a reasonable ceiling height, you will practically have to use the full 6m. The remaining 2.50m (minus the thickness of the roof) would then be exclusively under the ridge. You can squeeze a few boxes in there if necessary, but the space will not be usable in the proper sense.

We have a similar configuration with 6.00m eaves height and the roof ridge at 9.05m (25° DN).

Technology in the roof is possible, but that also means no cold roof.

since my previous plan so far provides for a house with a hip or tent roof

And now no longer - why?

Hip / tent means: no gables, only slopes. So rather not likely to gain space.

Max. wall height from top edge of floor slab: 6.0m Max. ridge height 8.5m Roof pitch: with wall height 4.5 to 6m 15-25 degrees

That doesn’t exactly suggest a lot of attic space at first glance. Hobby room, certainly not; more like an attic for Christmas decorations, winter coats, holiday postcards...

Storage room with standing height and a living upper floor I see connected with an OR, not with an AND. Basement at least has the charm of not costing above-ground height.