Hi Alice,
Ok. I'm not sure this is a best practice. If a message absolutely has to reach all of its recipients, I'd consider using a different pressure rule for that one.
First, please go through this documentation about consistency rules (pressure and capacity rules): https://docs.campaign.adobe.com/doc/AC/en/CMP_Campaign_Optimization_Consistency_rules.html
For your specific use case, recipients matching the pressure rules criteria are excluded at the moment of the analysis of the delivery. So re-trying to send the delivery would only retry for recipients to whom the delivery was actually sent (for example after a soft bounce, etc.). The delivery would not be analyzed again, so the recipients excluded the first time would still be excluded.
A workaround would be to create another query after your delivery (using a wait activity to process it 'x' time after) to target the recipients who did not receive the first delivery but were part of the initial target, and to deliver another (or the same) content to them.
Florent