Thank you for your explanations cryptonit!

I think a two tiered masternode configuration with a collateral of 15k and 30k DMD could be fine for DMDv4.
The increase from 10k to 15k should prevent a too large number of validators, to keep honeybadger highly productive with up to several thousand tx/s.
Furthermore long time DMDv3 masternode owners should be able to get another 5k of DMD before v4 kicks in, if they hold their coins.