Does anyone know what the reduced baggage benefit will be? For instance, if a Mosaic 1 has Jetblue+ card, will they get their Mosaic bag in addition? What about for international Blue fares which already include one checked bag?

I really hope the answer isn't "no, in either of those situations, you get zero benefit for being Mosaic." If so, there's literally no reason for anyone to try for Mosaic 1 this year (if they know they can't make Mosaic 2 or higher). Either get the $99 credit card for a free bag on all bookings and/or use your United number, where it will be much easier to attain Silver status and you'll get almost all Mosaic 1 benefits on Jetblue anyway.