As the AT-patrols are part of the Musti section (Musti has crew of 6), maybe reduce Musti crew to 3 and add an AT-patrol to the section? The problem this way would be that Musti's combat survivability would drop dramatically, especially vs. bigger calibers and artillery. Other way of portraying it would be to add APILAS as a 2nd weapon to Musti section, but then the patrol would not be mobile.
"In addition to that there's a somewhat rare squad type called Anti Tank Squad. I'm not sure if they are present anywhere else than the Musti Companies. It consists of two AT Patrols, each lead by an NCO and most of the time used independently from each other."
-Well this one is not rare, as "Sinkoryhmä" is also found in each infantry/jaeger Company. Also the Jaeger Bn AT Platoon is made up of 3 of these squads. I've used AT-patrols to form these squads as they almost always work as patrols of 3. So in companies you find 2 patrols under CO, and in Bn AT platoon you find 6 patrols.
Zip
PS. Look what the cat brought in... Looks like a Leopard 2R assault breacher and AMOS on AMV with 3-colour camo
(see the attachments, contains JPG images)