I really wish I could offer a good suggestion here, as I see how this could be a useful feature. Problem is, I really can't see how we can break an X3 page's gallery into "segments" and mix with text. First of all, that would require some advanced panel settings to break gallery after "image X", and inject some text with html formatting. Furthermore, that would essentially mean you have multiple gallery layouts ("justified" etc) each which need to get rendered separately within its gallery "block".
My best suggestion for this by far: Why not just use your CONTENT section? You can write any text, and then add one or more images:
Of course, this would only work for VERTICAL layout images (not grid), but you can still have them support the POPUP on click. You could also setup all images to be a "group" [ref] so that you can navigate between them when clicking an image. You would also need to HIDE every image in the gallery section, or hide the gallery module itself, else your embedded images would repeat in the page's gallery section.
If you wanted to get more advanced, you could embed the images within a block-grid (see content > templates dropdown for example).
Not as advanced as the gallery layout itself, but the most flexible way I can think of adding a nice linear walkthrough of images with text.
Optionally, you could simply use LONG titles and descriptions for all images in a gallery layout. This way, you could simply use the gallery layout. Consider a page like this or this, with much longer image descriptions. The advantage is you are still using the flexible gallery layout, but the disadvantage is that you can't "group" images and then add text.