DSLR is not really an option, how are you going to control it 1/2 mile out? Plus they are still large and somewhat expensive even mirrorless.
What is needed IMO is a drone more oriented to photography, not video. DJI has that in the Inspire 2, but at around 8K (that is will extra batteries and full range of lenses and their 24mp AP-C sensor). The Inspire is huge, loud and always draws a crowd. It's something I can just throw into a pack and hike 10 miles to get to where I want to shoot.
The M2 Pro has a OK setup but it's really needing some better design points:
1. Portrait orientation for gimbal like the MPP (huge for manual panos)
2. Less with less retrofocus distortion. (To see this just pan across a scene and watch the object elongate and flatten as they approach the edge of the frame, buildings, mountains etc.) makes a pano hard to construct (see number 1)
3. A sensor with better low DR recovery. The M2 Pro even at 100 ISO has about a 1/2 stop maybe 3/4 stop of shadow recovery. It does better with highlights, so exposing to the right helps. But you still need a lot of images to handle a high key scene (sunrise)
4. More bracketing exposure steps, at least 1 stop per bracket instead of .7. This is so simple to change in firmware DJI just refusing to do it, shows their lack of understanding of needs of a photographer.
5. Interchangeable lenses, (at a reasonable cost and weight). P5 platform rumor was just that, and it if was based on that drone not what I want as you see props way to often and in all true panos where you are looking up.
6. Better communication with Adobe for color profiles as the current ones are limited for the M2 Pro (unless the last LR/ACR update changed this) currently you only have the Adobe defaults and the Modern series none of which are that good.
7. Better solution for manual focus. There is no 100% view for checking your focus as with any DSLR, and this is critical for the best focus. Currently if you zoom anywhere close to 100% view is blurred and checking a image on iPad or
SC again you can get up to 100% without blur
There are more, but my point is there is a lot more needed than DSLR vs Gimbal. The former is not really an option unless you want a huge, loud, heavy, drone like M500, I don't and the current gimbal drones just need more development.
Paul C