There are currently 18 teams in the top two tiers of the WSL, which is being increased to 20 clubs by the year 2017.
"Where we really want to get to is 24 fully-professional women's teams playing in the league," Brazier told BBC Radio 5 live sports extra.
"But we need to do that slowly, so the clubs can become sustainable."
Sheffield became the first team to be promoted to WSL Two when they beat Portsmouth in the Premier League play-off final, having also met the WSL's licensing requirements.
In addition to being able to prove their financial solvency, clubs applying for entry to the Super League must show they will attract an average of 350 spectators in 2016, increasing to at least 400 in 2017.
"We have a licence system within the WSL and the reason for that is to try and influence and shape the way that money is invested into the game and do it slowly, in a measured way," Brazier added.
"By having a salary cap in place, it means that we can also ensure that money is invested off the pitch, as well as on the pitch, in salaries.
"Building things slowly is really important, because we want it to be sustainable."
The Women's Super League could be expanded to 24 teams in the future, according to the FA's head of women's competitions, Katie Brazier.