the way that it works in sovryn-rollup is aggregation is permissionless and anyone can run an aggregator. Indeed the only benefit of posting your transaction through an aggregator rather than sending it to the L1 yourself is to amortize the fixed costs (e.g. Ethereum has a 21,000 base gas cost per transaction but rolup transactions are generally in the 2,000 gas range, so by batching you can reduce the overhead).
The sovryn sequencer is a privileged aggregator that can guarantee the ordering of its transactions and thus has the ability to put them ahead in line (in a short time window) of other aggregators’ transactions. So it can slow things down but not censor as anyone can post a transaction on chain that will be included.
Fair ordering protocols come in very useful for distributing the sequencer and making sure the sequencer cannot frontrun/reorder/extract MEV.
The initial sequencer will be run by us. So there won’t be frontrunning since we won’t do that but fair-ordering BFT gives you that guarantee without having to trust us at all.
We don’t love the idea that the sequencer can reorder transactions and extract MEV and we will therefore distribute the sequencer and use a fair-ordering BFT to ensure that the Sequencer does not re-order transactions.