S and V are still inversely linked, and S is linked to the price of the currency. So as Velocity of money increases, the price will too.
Unless you have an increase in spending, generated by either increased value or increased userbase, no.
If you plan on breeding an infinite number of users at a constant rate, yes.
Is it safe to linearly increase M alongside U?
No, as it would mean a constant value for S/V which would only happen in a controlled economy.
Your formula basically changed the average transaction price level for users * token spent in the basic economic formula, rather than making a median at the average transactions you're dealing with users.
I would argue that a new user is worth roughly as much as a current user, where current user includes those users who have claimed and dumped their currency as I'd argue the same percentage of new users will do this.
Of course, because you're not counting users as individuals but you're deliberately treating them equal, so unless you want to throw in variables like purchasing power, value or amount of transactions possible in their group, yeah, all are equals by your proposed formula.
The new user is not given his currency upfront but rather must link to 50 friends.
I'm not really getting this part so I might be mistaken but be careful what an x50 number will do in just a few rounds of multiplication.