Theoretical (and practical) way they could reboot Warehouse 13 as a sequel with less initial effort:
- Pete and Claudia are the new top agents at the Warehouse.
- Pete is the new Artie, in charge of day to day running of the Warehouse and is generally the top dog around the place. He still hasn't read much of The Manual. ("I'll get to it eventually. You know, like after I die.")
- Claudia is still training to become the new Caretaker, but has put that on the back burner until they have enough hands on deck.
- They bring in two new agents as the primary field agents, but Pete and Claudia have issues leaving them to themselves on missions so we get a lot of A-team/B-team from the outset. It's possible that the newbies not working out is what brings back some of the old cast.
- Everyone else has either retired or moved up the ranks: Artie is a regent now. Myka split with Pete years ago and moved in with Helena, trying to live a normal life. Steve "retired" but is the new B&B owner. He couldn't step away completely.
- Myka is happy with Helena away from the Warehouse, but is still Pete's number one go-to for field assistance. A lot of her help is off-screen (at least initially). Helena fills in a lot of knowledge gaps, as well.
- Steve is willing to assist in missions moreso than Lena did, but his partner/boyfriend/husband doesn't like the danger so he keeps his direct involvement to a minimum (at least initially).
- Artie shows up to support the team from an administrative position (at least initially).
- Mrs. Frederick is still around, but rarely seen, as per usual. She does like having Artie as a regent, though.
Reasoning: Anchoring the show with Eddie and Allison makes the most sense, as they seem to be the leading actors behind the reboot concept (and their characters sticking around are the most plausible). Bring in the old guard as actors' availability and desire to return change, from cameos to full series regulars if desired. Not everyone will have the time necessary to return to a serial like WH13. This lets them help out however they want to, or work their way up to full-time casting, while still having that connection to the original cast.
A "reboot" is such a scary concept to a fandom. It could start a whole new canon, or continue the one that exists. Hopefully they find a way to include as much charm and nostalgia as they can while making the new concept unique and good as a stand-alone.