As profiles and diverts are very basic today besides all normal smarphone options there should be options for addtional profiles (timed) with built in controll of data roaming control.
Home network with unlimited data plan configured as you want with widgets, E-mail sync.
Editable roaming profile for EU where again the charges are high but not so bad.
Rest of the world where you can put all dat only Wlan an e-mail as we want, manual or hourly based on individual needs.