Why 35-27k though? the handicap system would be a bit messed up. I think the good old 25k will do since OGS already has a wider range of rank than other servers, most start at 18k. Maybe instead of a two-tier system @50_kyu suggested, having a 5 tier (or some other number) system will help out the dan players to settle in the server quicker. People at Tier 3-5 probably knows their rank already, for people wondering if they belong to tier 1 or 2 maybe a diagnostic tsumego test can be provided.
Here’s my suggested breakdown, so instead of asking people to select from a large range of rank they select from a few tiers to help them settle to the right rank as soon as possible without interfering with other regular users.
Tier 1: 24k-18k (knows the rule, limited game experience)
Tier 2: 17k-12k
Tier 3: 11k- 6k
Tier 4: 5k- 2d
Tier 5: 3d+
Another issue I thought of with default 13k rank is… what if the new player just don’t play any ranked game(maybe they want to wait until they get a bit better to start playing rank, or maybe they just accidentally unchecked the box because they don’t know what it means), then they will keep getting auto-matched to 13k.
Fun Fact: Krnzmb’s alt is still at kyu level after a few ranked games and a bunch of unranked. Since playing ? player will also affect your rank nowadays, I don’t think his regular high dan opponents would be happy if he use that account to play them and cause them to lose a lot of points.