It seems the dev’s are adamant about keeping dailies so with that in mind:
There should be a weekly Una’s for completing three legion raids.
The reward for completing it should be equivalent to doing 7 Una’s dailies.
What this would do is alleviate some of the FOMO people have of missing dailies, veteran players with establish rosters/many characters/many unlock raids will complete the Una’s task as part of there weekly raids. Players that are new/less available raids can do the una daily till they get to the point where is beneficial to complete it as part of weekly raid.
*Completing a daily Una will forgo your weekly Una/Vice versa