In the next hardforking change we should add a separate Merkle tree to Elements blocks, committing to

• The Blocksigner policy (signblockscript), encoded as a Script
• The Watchman policy (fedpegscript), encoded as a Script
• An arbitrary bytestring (which Liquid will use for its PAK list), encoded as a byte vector

We should further change the consensus rules such that whenever 4/5 of the most recent 4320 blocks (30 days of 1-minute blocks) commit to different parameters than the current consensus parameters, the committed parameters become the new consensus rules -- with the exception that peg-ins using the old fedpegscript will continue to be recognized for another 4320 blocks to give claimants time to adjust.