Who do you think Daeron I would have married if he didn’t die early?

I don’t know. The Targaryen practices of marrying their kids to the worst people possible seem to have hit pretty hard in that generation – you’d think the logical step is to marry Daeron to Daena who adored him and Baelor to the pious Rhaena, but for some reason Baelor was married to Daena and neither Aegon III nor Viserys II made provisions for Daeron I.