It just wouldn't make economic sense to start that sort of workshop from scratch today, unfortunately. Companies like Clifton, Flinn Garlick, Ashley Iles, Ernest Wright, etc... only work because they already have the premises, the equipment, and the know-how from a century ago. It would be wonderful to be able to have more British manufacturers, but I imagine that these existing businesses are only just scraping by themselves due to low demand for premium tools. This is clear from how retailers like Axminster are struggling to get by.
Hobbies aren't as popular as they once were, as fewer people have spare time to spend on hobbies due to toxic work cultures in modern workplaces meaning people work much longer hours, and people are working many more years than they would have previously, so there are many fewer retirees than there were twenty years ago. Plus the fact that there are a lot of people who are struggling to make ends meet, so they do not have extra money to spend on luxury items such as tools.
I've been thinking hard about this. It's obviously more complex than the initial idea and as I have no experience of running a business, I'm open to correction on just about everything. However, here goes:
My first thought was something more along the lines of a one man and his dog set up or perhaps a group of like minded people each taking a different stage of production, initially in a leisurely, free time sort of way. There are of course examples of this e.g. Philly Planes and HNT Gordon in Australia. As far as I can tell, they are serious commercial ventures but are not run on an industrial scale.
The next step up - while retaining quality - are smallish to medium firms like Clifton or Lie-Neilson where quality is still excellent. I presume that Veritas is a step bigger but quality is still maintained. The key word is quality because it seems to me that as soon as you go mass market, that will suffer or the tools become electric and expensive if you want reliability eg Festool, Mafell.
The other thing is that most toolmaking, unless you're doing wooden planes, is going to be principally a matter of metal work (of which I know nothing other than the odd bit of rust removal and sh***ening). So suppose you wanted to make e.g. a hand drill. There aren't that many components but the gearing and the chuck look a bit fiddly. Must be doable though, because it's been done. If the idea was to start small and the people involved weren't going to live from it e.g. hobbyists/retirees, I wonder if with small production rates of high quality kit, you could start to establish a name and more importantly a demand for the products, thus facilitating the next stage of putting the set up on a more commercial basis. I reckon the key is to win customers who are knowledgeable and don't mind paying for quality.
Finally, I wonder if the Americans are more inclined to take on such projects. Just consider The Lost Art Press. They decided to address the niche market of woodworking and other crafts books. They did, however, insist from the word go that the books would be made to the best old-fashioned standards. Now they regularly reject takeover offers from big publishing houses, the sort of firms which abandoned physical quality in their books years ago, thus creating a gap in the market which LAP plugged and is flourishing as a result. Similarly Stanley abandoned hand tools but now, having noticed the revival in hand tool use amongst hobbyists, they seem to be playing catchup but their products don't seem to be rated as highly as those of their rivals I mentioned above.