Somerset CCC, Gloucestershire CCC and the University of Exeter have joined forces for their bid, with home games played at several South West venues.
Lancashire confirmed their interest in July but have now asked to be involved in the T20 tournament next summer.
There were 28 bids made to the England and Wales Cricket Board by August.
"Our objective is to play matches at Taunton, Bristol and other venues around the region," said Somerset chief executive Guy Lavender in a statement.
"We not only want to produce an outstanding team but also to use this as a vehicle to engage more participation for women and girls right across the region."
Lancashire Cricket Board vice-chairman Bobby Cross added: "This is an unprecedented period in the development of the game in this country.
"We see WCSL as a fantastic opportunity to explore the potential for the next generation of young cricketers to push the boundaries and to give the national side a bigger pool of talented players challenging for places."
Hampshire's Ageas Bowl has also confirmed it is bidding to host a side in the inaugural Twenty20 event next season.
An announcement regarding the successful bids is expected by the end of January 2016.
A South West consortium and Lancashire are both bidding to host one of the six teams that will form the new Women's Super League in 2016.