My personal idea for a "solution" here would be two XP bonuses for frontlines

One much-smaller-than-current XP bonus for your first participation on Frontlines for the day
One similar-or-slightly-larger-than-current XP bonus for your first *win* of the day. Stacks with first match of the day if they are the same match.

Still encourages people to queue for Frontlines for their XP bonus, but incentivizes even the "i dont like frontlines" people to try in order to hopefully have their first match also be their last of the day.