Like many others have said, games such as Call of Duty decided to go with a small portion of his game as free to play, and I am talking about COD:Warzone. Players liked the core game, gameplay, etc and decided to buy the whole game. I think the same marketing strategy could also work for SOT.
With the addition and announcement that Sea of Thieves is coming to Steam I think this would be an amazing opportunity to bring life to the Arena servers, decrease waiting times, fill sessions and gain even more players in the long run in Adventure.
Matchmaking ranking(MMR) would also be welcomed, pairing players of the same skilllevel against each other to help them understand and grow their skill.
This decision would ultimately help shift the focus and attention to the game once again. The SOT community would benefit from this move as the player base would grow, at least in Arena and would encourage streamers to give the game one more shot because it's "on the spotlight". Pair this with the steam release and it would be perfect.
Nonetheless for this to work servers would need to be prepared for such an high influx of players DAY ONE.
Think about it :D
