Thank you for your suggestion. This is not currently on our road map.
As suggested by others, customers are implementing this pattern using the same container with a partition key per tenant or a synthetic key with the tenant id and one or more other properties.
Will mark this as unplanned and leave open and will revisit this in future planning cycles.
Thank you for your suggestion and votes.Peter Lea commented
A lot of service providers would kill for this option. Currently we can't consider moving to cosmos because the risk co-locating tenant data is too high.