By virtue of its nature a window seat is a box like build in that "sits" within the space of a window...so I'm not sure I'm understanding your exact question... If you want to have custom made window seats installed they can easily be built with storage, as the top (lid) would lift up on them. A standard height would be about 20 - 25 inches and if you want them kept "clear" of debris so as to not distract from the views, you can keep some comfy pillows inside of the storage area for each "seat." The total height can include a 2 to 3 inch dense foam pad to sit on top; covered in a fabric that complements, or matches your decor..colors of the drapes (to cause it to blend in) or something contrasting to stand out a bit. You can also pick colors that BLEND into the ones you SEE outside of the window, if those are complementary to your inside colors! Remember too that the materials composing the Window Seat do not have to be "natural warm wood." If your decor is more hard, straight, modern..you can make your window seats to match...Metal..distressed or gleaming can be used....or incorporated into the construction, IF it adds to your existing decor style...also wood that is painted..gloss or flat or semi-gloss can be used! Traditionally, a Window Seat is seen as a "warm,cozy" spot to sit, read, gaze out the window, daydream. But not all "typical modern" designs would be aligned with the concept of "Warm and Cozy!" Ultimately you want to work with your builder to create what pleases you most. There is no reason you cannot have exactly what you want, looking exactly as you want it too look!