usually vias don´t have thermals at all.
(Only THM pads).
Thermals improve THM soderability when a pad is connected to a large copper area.
Vias don´t need to be soldered, therefore there is no need to use thermals.
(Maybe there a special conditions...that recommend thermals on vias. Then tell us)
It´s very clear:
* You know: thermal prevent heat transport, but you expressly want heat transport --> don´t use thermals
* I said: "there is no need to use thermals." --> don´t use thermals.
Go through the links in the box "similar threads" below.