Just figured it out
Open "database.bin" find "f1teams" and in there find "id" column. For example, mercedes has 22 and marussia 30, swap those two and voila u can start with mercedes
P.S.: after changing ID u need to restart profile because it cant find teams u changed, so u do young driver test day 1 again and u are ready to go.
This is just fast change so no idea if it changes speeds, ai behavior etc of edited teams (so far it seems to be working no problem - u wont get tier 4 speeds/team mate times).