I'm guessing Revell made the A-1 for a number of reasons; they had access to two real ones, restored or under restoration, found as they had been in 1940. The kit was produced in time for the 70th anniversary of the outbreak of WW2, and the BoB. Also, there were no other A-1 kit versions around of this important aircraft, not since Frog in the mid 1960s. It will/would probably be easier to engineer a kit to be released later with parts to make the A-4 / A-5, than to back-engineer to the A-1, plus, as has happened, a wealth of aftermarket parts would be expected for other versions.
In other scales , there have been numerous kits of the Ju88 in versions other than the A-1, and, until Revell released their kit, none had the benefit of an actual aircraft from which to take measurements and data, some of which has been able to prove the location, or otherwise of certain fittings, such as dive brakes.