I became aware of a limitation of the use of a typical touchscreen-based remote control in some situations when compared to a traditional remote comprised of physical dials and buttons, in that with the tactile sensations of typical controls, you can operate the controls whilst viewing the main display which forms an efficient feedback loop, informing subsequent adjustments to the controls.
For many situations this might not be of any real consequence but for controlling photo and video editing applications, it's an important consideration.
You can buy physical knobs and sliders which stick to a touch screen using suckers but they're pretty expensive and/or chunky, blocking a lot of the screen off.
My half-baked idea is maybe a removable screen protector film which could have braille-like indentations pressed into it by applying the film to a suitable surface (maybe 3D-printed?). That would provide some tactile feedback but still allow the entirety of the screen to shine through and not be a hassle to set up and remove when using your tablet for something else.
These touch screen joysticks meant for mobile gaming are cheap but still block some of the screen and would be a hassle to set up and remove each time: