And you wouldn’t need the pack sizes to change at all.
In the UK we have products in both round metric and round imperial sizes to this day.
Just look in your cupboard and you might be surprised at how many things are 454g, 340g, 227g, 113g or perhaps 568ml and 284ml.
The label might be metric but the pack size is 1lb, 12oz, 8oz, 4oz, 1 pt and half-pt.
Likewise, if something is 100g, there would be no problem labelling it as 100g/3.5oz or if it’s 200g it can be labelled 200g/7.05oz.