The research for improving the production of other kinds of vitamins is more active, by trying to either discover or create bacterial strains suitable for this purpose.
A serious problem is that unlike the production of traditional food, the production of vitamins and nutritional supplements is concentrated in a few countries, and mostly in China.
So if overnight everybody would become vegan, then suddenly most of the world would become nutritionally dependent on China.
Ideally every bigger city should be able to produce the vitamins needed by its inhabitants, like it is able to produce other staple foods, but we are very far from this when entire countries may not have any vitamin production facility.
Humans also produce creatine, choline and taurine, but for these three there is convincing evidence that the internal production is not sufficient, so for vegans it is beneficial to take supplements with them.
It is likely that the internal production of K2 is also insufficient, but I have not seen yet any conclusive research results about this, because it is very difficult to control all confounding factors.
Even if it is not certain that this is needed, it is prudent for vegans to also take vitamin K2 supplements, along with the other substances known to be missing or insufficient in vegetables (vitamins B12, D3 and K2; DHA and EPA; creatine, choline and taurine; iodine, selenium, calcium and sodium).
I do not believe that paying such prices is rational, so for many years I thought about eating only vegan food, but I could not see any way to get enough proteins without gaining weight.
I could switch to vegan food only after I have discovered that I can make a home-made bread that is highly enriched in protein by removing about 75% of the starch during a 6 to 7 minute washing of the dough. With a longer washing time it is possible to separate completely the gluten from the starch, but I am not willing to spend more time every morning with breakfast preparation, and this is enough to provide on adequate protein to calories ratio.
For Omega3, the only good alternative to fish oil is Schizochytrium oil. A few years ago, it was 8 times more expensive than fish oil, but the price has been declining slowly and now Schizochytrium oil is only 3 times more expensive than fish oil (e.g. with taxes and shipping included, EUR 300/L for double concentration Schizochytrium oil vs. EUR 50/L for cod liver oil). This is still very expensive, so hopefully the price will continue to decrease.
Vitamin D3 is normally made from sheep wool, which seems a perfectly sustainable source. There exist products which claim to contain "vegan" D3, but until proven otherwise I believe that this is a scam for extracting money from naive vegans.
The "vegan" D3 is claimed to be extracted from some kind of lichen, but it is irrational to pay money for such a product unless the vendor discloses which is the exact species of lichen, whether it is a wild lichen or a cultivated lichen, how it is cultivated and how the vitamin D3 is extracted from it.
If the lichen is not cultivated, but wild, that is not acceptable. Wild lichens grow extremely slowly and exploiting a species for vitamin extraction is guaranteed to cause the extinction of that species in a short time.
This is called seitan and has been a meat replacement for at least a thousand years. You can buy it in the store. Hell, you can even buy wheat gluten itself right from the store and make your own without all the washing.
The one benefit of pea protein is that it doesn't foam up like whey based alternatives in a blender and upsets my stomach less than the whey.
Chalky as hell though. 3/5 stars.
Pea protein has 78/100g protein which sounds like a reasonable replacement for whey protein isolate (89/100g) or other animal sources. Not saying you should eat pea morning 'till evening but supplementing just protein powder is an option, too.
What vegans may have trouble obtaining from non-animal sources are vitamin D3 and Omega3 fatty acids.