It can work, but most times I've tried that the escorting beam defence boat ends up the first target, and since the only support it can get is AMM, it tends to die. I've worked Area defence laser boat + GC Escort boat pairings on it and it works better (or you could add both to the same boat).
I wonder if it might be more effective if you wait until the missiles are incoming before detaching (i. e. targets have already been committed). Stop/reverse the main body for a couple of increments until you achieve the desired spread.
If you have the resources for build fleets with that complexity it can work. Personally I try to stick with the KISS principal as much as possible.
I don't see how that greatly complicates fleet design, assuming you have beam-armed PD escorts in the first place. I suppose you would need bulkier fire controls than one that is strictly limited to point blank. I guess it would depend if you wanted to dedicate a design to that specific role or one that could operate in either 'ring'.
I simply like to have options (for RP reasons if nothing else) for different fleet doctrines; including ones that might be sub-optimal. Optimal is easy (for me, that's carrier based missile strikes backed by a size 50 sensor).
