Whether it's compelling depends a lot on pricing. After see what they charged for a RK3588-based machine, I'm not too optimistic about that.
I don't love the idea of proprietary docking options. I'd rather just a standard Thunderbolt port, as mentioned.
The last major factor is going to be how they configured its power limits and how well-mannered its cooling solution is. I often override the power limits of my laptops, since I'm easily annoyed when their fans get too loud.
Is it a NUC-killer? I doubt it. It's nice to see them trying to innovate, but my fear would be that they're hoping to leverage a few innovative features to justify a much higher price.
One of the interesting peculiarities of the Khadas Mind is that it has a built-in 5.55Wh battery that provides some extra protection during power loss and allows one to carry the device around in sleep mode without having to shut it down.
I suspect the built-in battery isn't aimed at portability, but is really meant to address users in places with unreliable power. If you had lots of brown-outs and other power problems, it's likely you'd either have a UPS or use a laptop. Perhaps they're trying to present a 3rd option, but if it has no way of powering a monitor, then you're still somewhat reliant on power returning (or I guess the machine could hibernate, when its battery is low enough).