Um, no, not so much.
* https://www.instructables.com/id/Homemade-Vape-Pen-e-cig/
* https://www.instructables.com/id/DIY-Electronic-Cigarette/
* https://hackaday.com/2014/09/13/homemade-e-cigarette-vaporiz...
* https://modern-crafts.net/basics-for-building-your-own-box-m...
Note: mechanical mods are a great way of setting your batteries on fire. Most regulated mods are built around a relatively small number of platforms (https://www.evolvapor.com/), but there's no magic involved and if there aren't open-source hardware now, there will be soon. If you don't care about unit-cost, size, and scale, I'm absolutely sure any electronics hobbyist could build something as functional as most of the commercial platforms.
I can see two obvious consequences of banning e-cigarettes:
1. The Arduino brigade whining loudly that they can't get the parts for their plant-moisture monitor "because you could build an e-cig with that."
2. A rise in trouser explosions from improperly constructed vapes. (Contraband rarely gets UL listed, right?) I would like to officially nominate the term "jake leg" for the resulting limp, in honor of a previous attempt at regulating morality in the name of public health.
P.S. https://www.youtube.com/watch?v=4KA40gBpDhc