Fair point, I'll drop "just raise the cap." You're right that the cost is roughly quadratic. TSS keygen and signing are O(n²), CometBFT vote gossip is O(n²), and every churn runs a fresh DKG on top. That's exactly why the set is capped and the vaults are sharded. It's a principled constraint, not centralization.
So the path to A isn't more nodes. It's two things: (1) spread the existing ~100 slots across many independent operators with well distributed bond, and (2) harden the RUNE pendulum. Actually raising the cap would take a real scaling advance in the signing scheme (FROST, DKLs) or committee sampling, not a parameter change.
And third, start thinking about post quantum. Your vaults are large standing pools of real BTC and ETH at known addresses with exposed public keys. TSS does not help here. Splitting the key protects against classical theft, but Shor's algorithm recovers the secret straight from the public key, so threshold custody is not quantum safe. A state actor with proper resources and a working quantum computer would treat those pools as exactly the honey worth spending it on. The catch is you can only sign what Bitcoin and Ethereum verify, so the full fix waits on the base chains, but you can start now by keeping less idle value in vaults, rotating exposed keys faster, and planning a migration path for when PQ signatures land.