I'd rather it was an hour, and would be quite happy with Ten's original 30 minute dailies tbh. Treat 'em mean to keep 'em keen. Keep them wanting more. People are sick of the huge commitments the networks are putting on them. Perhaps a 30 minute evening show and a 30 minute late show would work.
In this new streaming age, it makes even more sense for BB to go back to the Ch10 format.
You could run 30min daily shows Sunday to Friday in between the news (which doesn't need to be 1.5 hours) and the project. For those who want more, they can then upload an extended and uncensored cut to either 10play or Paramount+ (depending on how they want to run their online strategy with live streaming etc).
Sunday: 60min Live eviction
Monday: 60min Live nominations (I really liked the glass box from ch9 - added to the suspense)
Friday: 60min Live Friday night games
Feel like you might have room for another 60min episode on a Tuesday if you can come up with a good reason for it. Maybe an uplate or a panel show. Not keen on a challenge ep ontop of the friday night games. These 60min shows are probably more suited to 8.30pm, which leaves room for 10 to schedule at both 7.30 and 9.30 throughout the whole week.
I would run the season from the Sunday following the grand final (AFL) through to the week of xmas. Those ~80 day seasons were about the right length without dragging.