Yeah you can never have too many switch ports available.
But vs bridging, why don't you just create a new network segment and route between them. Say your wireless lan segment, do you have a AP plugged into your current switch?
To be honest you could prob use the w7 vm there, its pretty straight forward in bridging interfaces vs pfsense
But bridging is not a good solution even if no issues with it, but creating a new segment make sense in correct network design.
Since your using pfsense as your router - I have to assume you have some old wireless router laying around your using as an AP currently - which I guess is plugged into your switch you need to free up a port on? Break your wireless out to its own segment. Use pfsense to firewall between your lan and wlan. Now even if your wireless is compromised, you let a guest on with some nasty worm.. Your lan is secure.
Example any wireless clients can only talk to my ntp server, and the internet and dmz in my setup. They can not talk to lan. Since they really have no reason too.
Think of this way, when you break out wireless to its own segment, all your wired boxes broadcast traffic is not now going out your wireless network.