Have a bunch of 3D printers and DIY.
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That's for last year's war. Nowadays, drones have SIM chips in their phones from the local they are visiting and pretty high-resolution cameras - not to mention anti-electronic warfare stuff. Toss in a bit of AI along with terrain-following software assuming thee GPS signal will be jammed. Of course there is also control software to run the thing as well as whatever passes for engines (jet, quads, whatever). Sure, you can DIY as long as you can keep getting deliveries from Alibaba.

Back “in the day” I did a DIY conversion of a Bridgeport milling machine using bits and pieces acquired on eBay. It took 2 ½ years of evenings and weekend, the controls were completely different than anyone had ever done before and it way out-performed a commercial factory-built unit. Afterwards, using the knowledge I had acquired, I could accomplish the same results, using stuff I wasn’t even aware of when I started, over a long weekend (as I proved to myself by converting a lathe).

The point is, I would still be able to built it the first way if I had to, but the second creation required all sorts of specialized gadgetry (which a 3-D printer couldn’t have helped with).

Jeff