ADG had a version published from Australia, (they're the AUSTRALIAN Design Group, ya'know.) It didn't get wide play because of distribution issues.
AH signed a deal with ADG, sold EiA in a box, and it was relatively popular. But ADG made some rules changes for simplicity.
The General (an AH publication) posted some optional rules, some errata. Mostly common houserules that people play. AVP was introduced in a General article, I think. It was very unbalanced.
AH started going downhill. (Essentially switched from strategic games to beer & pretzel games.)
EiH started, 1.0 was essentially a re-write of EiA with holes filled. (such as retreat paths and stuff.) Some limited new ideas were introduced here, such as depot limits.
EiH 2.0 came out, with lots of new rules, lots of complexity, and totally unbalanced. (British Homeguard, etc.) 1792 scenario.
AH went belly up and sold to Hasbro.
EiH 3.0 came out, which is a simplification of 2.0, still somewhat unbalanced IMO. Concept of changing OOBs was started. I think ship-building locations were introduced here.
EiH 4.0 came out, which is essentially 2.0 on steroids. French revolutionary track, different unit types (Islamic Infantry, galleys), etc. I think it ended at ~70-80 pages.
EiANW started development.
EiH 5.x came out, with more complexity, and more of a focus on the 1788-1815 GRAND-GRAND campaign. OOB Morphing (actually started in 4.0) is carried on to a bigger extent. French Revolutionary track got more complicated.
Lives change, games change. EiANW should have picked either ADG-EiA, EiH-1.0 or EiH-3.0 to develop, but I would have liked a possibility for the 1788 uber campaigns. But hey, you can't get everything. The argument for the later versions of EiH is that we don't need a huge space for all the tracks and OOBs and such, we've got the spreadsheet. The argument for developing EiANW using EiH-3 was that there are a lot more things the computer can simply keep track of for the player, so the complexity issue isn't there all that much, and EiH 3.0 simply plays better than the AH version.
Light and Heavy ships have been in EiH 2.0, and I'm certainly satisfied that they work. Balance is a different issue, and ship counters have changed over time. (For example, EiH 5.2 have size 10 fleets, which can often be a mix of H and L, and multiple fleets can be used to transport a corps.) Realism is also a different issue, but I have never approached EiA with an eye towards realism. Instead of individual ships, it may be better to model factors instead. But everytime I proposed that, I got shouted down.

