There is no existing gearswap that would make Calmecac a good TP option for legs that i know. They are just not great.
Since you bring up Af3+2 legs.. i guess you wont have Thaumas and probably no Salvage+1 so the basic TP Setup would be Af3+2 Head/body/hands/legs+Relic+2 Feet, which alread is not capping haste,
and trying to cap it wont make it better. (Edit: I lied! Sigyn is almost allways better Feet then Assasin+2 :x) Changing legs to Calmecac make them worse, changing Relic+2 to Sigyn makes it less worse, but still worse. They are already worse the Af3+2 legs, and wont hold a chance against any other Legs a THF would TP in. And i wouldn't even consider those legs as a WS piece