IronWolf
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4e needs stats for defenses and attacks, since changes to NPC generation mean that just listing their gear isn't sufficient. It would be maybe 2-3 lines in 4e. AC/Fort/Ref/Will and something as simple as "Short sword: +7 vs AC, 1d6+4 damage". A lot of 4e DMs would add 20ish HP to each orc, to make them look like the orcs listed in the monster manual, but I think this would be a mistake. 8 orcs at 30hp each would be a slog. I'd keep them all at their listed HPs, though I might consider tossing another 10 or 20 HP on the strongest one, along with giving him better stats to make him more apparent as the leader. But now we're well into taste stuff, not required stuff.
It'd work for 4e, too, fairly easily. The DM would have to work out basic stats for the enemies, but it wouldn't be any harder than looking up what AC chain and shields gives in AD&D or 3e.
Considering the number of orcs, couldn't many of them be minions?
You are both right that there is enough framework here to allow a DM that wants to put the time in to tweak the encounter to their particular edition. We can do that now with nearly any module out there if the DM wants to put enough time into it. If I want to run the old Temple of Elemental Module in Pathfinder I can grab my old copy and get to work. Because I run sort of on the fly when it comes to encounter strength it wouldn't be all that bad.
But we are talking a published module that is expected to be run for any version. With that expectation I think you have to cater to the DM that just wants to grab the module and run it. No on the fly conversions or mechanic tweaks needed to make it work for their edition of choice.
If the DM needs to work out basic stats then the module has failed at catering to each edition.