Just throwing this out there... Why not a simple rule to require all shares to be held for at least 24 hours before selling? It would certainly change the game in every way imaginable.
Market makers are good for widows and orphans. You don't want your grandma to have to be careful with the day of the week or time of the day when she sells her stocks.
Tax wealth for all I care. But don't tax transactions.
(Btw taxing transactions would actually make financial speculation more profitable. Because bid/ask spreads would become wider and prices more volatile.)
Minimum holds are very different from trade taxes. (The latter is stupid for a variety of reasons.) Minimum holds would make market making more profitable.