I'm tempted myself as well. Will probably go for it. Before Arrastra came around, I was already dead set on getting an Orion. Now I'm a coins flip away from getting either an Arrastra or then Orion.
Tough choice tho, both seem like great mining ships, and I'd mostly be going around with an NPC crew anyhow, and Arrastra doesn't require as much crew. Orion doesn't require THAT much more tho. And Orion is Capital, which is cool.
As for possibly offering Hull D WB CCU during the next days, last year at least they didn't update the CCUs during the finale, the final CCUs stuck till the end of the event. So they might not be providing further new WB CCUs this IAE. Though it's worth noting that last IAE they also offered 15 CCUs for the finale (+ flight ready + BIS CCUs). This time we only got 4, so who knows, maybe they're doing new CCUs each finale day this year.