Yes many have swapped the cloth with full and partial leather Recarro's and vice-versa.
It is a direct swap. the ST1 has the hook-ups already for the airbags and electric motor in the ST3(full leather) seats.
Look in the for sale section or the wanted to buy (WTB) sections if you are interested in switching seats.
Also a couple vendors sell the Ford Racing Parts Recarro's, (with 'ford racing' logo instead of the ST logo.)
Hope that helps.