Assuming you don't want to split it tup:
In A1 place a file A1-packages.Rd which documents all sources of documentation
for A1. That can refers the user to the vignette in A2.
packages?A1
will bring it up this information help file.
You could also considering having a one line vignette in A1
Peter Ruckdeschel wrote:
> Dear R-devels,
>
> We have encountered a problem concerning a dead lock in the dependency graph:
>
> We have two packages A1 and A2 where A2 extends A1.
>
> We have one package vignette for both packages, but which should be included
> into package A1.
>
> So in the
