IMHO, and with all due respect, if Breece Hall is out for any length of time, the likelihood that Braelon Allen produces any numbers close to the statistical output that a healthy Hall will produce, is, very unlikely. They are two completely different backs, and you're trying to replace the production of an Alpha RB1 who has a ceiling of RB1 overall. Allen is a complimentary back, not a handcuff.
Across multiple High Stakes entries, I have only 1 share of Breece; I was not fortunate enough to be in position to draft him.
The particular League I drafted him in favors RB somewhat, and I chose him as overall RB2, behind CMC. This is a sizeable ROI on a large $ investment, local League, which I take very seriously. It didn't even cross my mind to prioritize Allen in the way I would prioritize Jordan Mason or Tyler Allgeier, had I drafted CMC or Bijan. Those guys are what I consider real handcuffs.
What works for me, in supplementing a Hero or Stud RB, is, amassing a depth of upside pieces with a path to snaps, that not only build me a stable of statistically viable backs, but serve to undermine the managers who draft the other rbs in the same caliber as my Hero/Stud.
It's my opinion, but I think Kyren has one of the weakest holds on a starting RB gig in top rushing offense in the NFL, and Corum overtaking him is a when, not an if, and that's a 50/50 soon out of the gate. He is better than Kyren.
Mike McD has already indicated JWright will get snap share right alongside healthy Mostert and Achane, and he was a surgical strike of a draft pick, perfect fit for that offense. He IS Mostert/Achane.
Allgeier and Mason and Montgomery are capable of posting Bijan/CMC/Gibbs #'s. One has done it already and the other is part of a system and the 3rd is some of both.
Or you can take 'lesser' RB1's who will dominate touches and are cheaper. Singletary is my favorite example of this type. Rhamondre, Swift, ZWhite, Chuba are others.
There are a bunch of other split backfields out there where the other half is going to get help, rather than morph into an RB1 caliber statistical generator if his partner goes down.
There is no true 'handcuff' for Breece, Taylor, Barkley, Jacobs, Etienne, Pacheco, Cook, Kamara, Walker, Mixon or Conner, which takes us through all the RB1's I'd consider headlining a stable with in 2024.
Every one of those situations is going to involve either a committee, or a back not capable of producing enough of an approximation to matter, at least IMHO (and yes, that includes Ray Davis, who I think people are sorely mistaken if they're chasing James Cook production from him).
Jaleel McLaughlin and Justice Hill are two others i expect to perform admirably in their offenses, in a pinch.
That being the case, well ahead of BAllen, I hunted all those guys during my Breece Draft.
I wound up with Breece, Pacheco, JCook, Singletary, JWright, JMason and JHill.
Annoyed I didn't get Corum or Allgeier, but you can't get 'em all.
My .02¢. Good luck!