I heard a fet based front end mounted at the headshell end designed and built by Peter Suchy in the mid 80's at CES. Only difference was that he ran an external power supply with wires running through the arm tube. I never saw this go into production though.
In fact in Japan there have been a number of these head shell based gain stages through the years. This one is one of the tidiest implementations I've seen.
If they had mounted it on top of the head shell there would have been no cartridge limitations.
Of course in the old days Ortofon had mini SUT's built into their low output cartridges in their integrated head shell with some models.