Support... The game can't survive without new blood, and this idea will clearly illustrate the value of ally plunder to new players and provide a growth window in a diminished ally market. Longer term, it'll allow new players to support each other and should help revitalize the ally market and decrease hire values a bit. All in all, a positive result.
Defo support as new players need help to get going because no cheap allies means they don't get decent gold. No gold means slow growth which means boredom. Also perhaps a proportion of the way through their new player period they could receive a notification to warn them that they need to get a decent ally before the spell ends to maintain max plunder.
Support. Definitely need new players to stay and sustain the game. This idea is a good way to attract and keep players
Full support, the lack of new players is a concern as is how many of them actually stay playing this game.