Liberation of Undermine gave us the option to chose the order of bosses we wanted to tackle. The obvious choice was Vexie, but you could also start at Cauldron, Rik, Stix or even Sprocket.
For mythic pugs & some guilds this was a huge advantage. You could tackle the “hardest” boss you wanted to try without the fear of getting a bricked instance id. Before LoU you killed the 1 boss, then people left after 2-3 wipes on the next boss and no new person would join.
The LoU system benefits both random pugs as well as guilds who need 2-3 fillers.
In Manaforge the boss choice only opens up after Plexus Sentinel, so everyone will get locked to the id.
I would thus suggest a system where we can use our nifty cloak (we go energy form) to bypass PS and be able to backtrack to him later.