While playing online friendlies, choosing of defence (Tactical/legacy) should be only available at Invite option. Opponent should not be able to switch within game or it should notify the other player. As Legacy defence has got more advantage on tactical.
This way players cheat playing with legacy defence but claiming of using tactical. EA please look into this. There is a reason legacy defence isn't allowed in FUT/online seasons/tournaments.
It should be controlled in Online friendlies as well.