Arena needs Phantom Draft format as everyday format or something near this. Not just random event on Midweek Magic (only some times per year, you are seriously???).
You can made schedule for this event - thats all: setup one-two sets for Phantom Drafts and rotate this time to time. One week - Phantom Draft Duckmourn, another week - Phantom Draft Ravnica, for example. Begin from something like that - not every set in Arena for this kind of drafts, but one-two-three. Free or for little gold (around 500-1000). Why Arena not have it for years - every day allowed someting one set Phantom Draft? Thousand of peoples dont install Arena becouse dont want to grind cards for constructed - they need start point, reason to first install the client.