Sure they can also make it so you have to have a license and pass an IQ test to reproduce. Honestly, it's not a half bad idea, but it will never happen. It is also possible that a giant asteroid hits the planet in the next year and kills everyone. You can't spend your life being afraid of ULTRA LOW probability events occurring. However, you should probably prepare for higher probability events to occur.
Banning or restricting (other than by age) nicotine base sales is a medium probability risk, taxing it is a much higher probability. Restricting other raw ingredients such as flavors, PG, and VG are ultra low probability. Why? First because so few people DYI, second DIY juice already has a choke point in the nic base, and finally those items have far too many other uses. Really, if you want to stop people from making lemonade you don't have to ban water and sugar, you only need to ban lemons. They can age restrict anything they want, unless they make the age restriction 100 years or older, I think most people here on ECF are going to be just fine with that. The government certainly isn't going to force companies to reformulate patented flavorings for this purpose.
The only real concerns at this point are the mods, the tanks, and the nic base. If you prefer pod type systems over mods and tanks and don't mind tobacco flavored juices, then really you probably have nothing to fear except the taxes. Personally I am planning on buying a few more drippers and tanks, and a case of raw DNA 75C boards. I can always make a mod housing out of nearly anything. Wood, plastic project boxes, etc. And I have some more stocking up to do on 1kmg nic base. Not to mention Mechs are crazy easy to make. Short of the apocalypse there is nothing they can do to stop ME from vaping. I will feel sorry for newcomers but this ant will be prepared.