Hey @koloz!
There is no formal gate to SIP creation, so if you feel it is ready to be formally proposed you can create a new post in the Governance Proposals category. If you have any code changes already identified it would be good to link those in the specification section so that implementation is clear (the staking SIP may be good precedent here, though that is not strictly necessary). Once posted, you are encouraged to attend DAO townhalls (the next will take place on September 28th) to discuss the proposal. It will need sponsorship from at least one council member in order to be posted to snapshot, at which point it will require a majority vote with a 5 million RARE quorum.