No inside knowledge here, but I suspect that MMP's efforts to release map and overlay bundles are a way to address this.
MMP are making an "effort" to create map bundles? They created one that is now sold out, with no apparent intent to reprint, and several other boards are also now unavailable because they have no apparent intent to reprint
them either. What is worse -- that MMP adopt a policy of printing new scenarios that make
no use of now-unavailable boards, or printing new scenarios that
do, knowing that many players will now be unable to play them? It's not the end of the world either way ("there are always plenty of scenarios to play") but if I was attempting to buy into ASL from scratch I'd probably be pretty annoyed.
As for overlays in a core module ... are there scenarios in the new
CdG that are unplayable even if you own all of the other
current versions of the core modules? (Noting that, of course, not all of the current versions of core modules are available to purchase.) A core module should not include any scenario that is
unplayable even if you own all previous MMP-edition core modules.
RS and
Yanks2 included some overlays specifically for that reason. (Similarly, no core module scenario should require the use of boards
only available in non-core products.)
The Overlay Bundle will be useful for some, essential for others, but it's still only a band-aid to patch a problem that should never exist in the first place. It's not a difficult concept: if you include a scenario in a core module, make sure that
all of the components required to play the scenario are available
somewhere in the existing core module system. If you can't do that, then don't include that scenario (publish it in a
Journal instead). Does the new
CdG actually violate that concept?