There are many 1v1 guilds, would be nice if it was possible to join a guild and have a personal guild queue. Just like the guild party system that existed back in Source 1. The reason is obviously that some guilds are exclusive and have high mmr players ready to 1v1, and with a guild queue you could meet randoms there instantly instead of spamming chat for a scrim partner.

And a small tournament system would be fun, as certain communities would love to rally behind their known players. Like PlayDota guild etc etc.
No item rewards, maybe just different color of text to their name in guild chat or a badge.