Scenarios don't use the OOB formations - as these have been chosen in the scenario editor when you bought the toys in the first place. OOB formation data is only relevant in a purchase situation (human or AI).
As to AI pick lists - see the link where these were discussed in the file attached
here but remember that playing with these is a real "black art" - and true hacker work as that is all I'm going to publish on the subject (no help etc).
But the MBT AI pick lists are variable, on both date
and also can be variable on opponent as well (so a simple investigation that USA uses inf co No 123 (without the inf-ATGM say) in the pick may only be good for say, 1966-84 and when playing the VC, but
not if playing the USSR!). And there are usually up to 3 alternate leg infantry, tank, and mech inf platoons and companies, determined on %age chance plus
remaining buy points available.
barges (carried in barge carrier and used for beach), barge carriers (river xing), HQ (both unit and formation No. 0!), crews, assault raft (carried by grunts in the river xing) are fixed in OOBs as is the 1000lb bomb weapon slot (for secondary explosions on ammo dumps), as discussed somewhere in the mobhack help.
Naval artillery (used in beach landings) - uses a set contiguous list of batteries (or mortar sections or field arty which will be carried in barges for some armies which don't really have a navy, but you
must provide "cover" units for the situation where an end user decides to beach assault with the Swiss, say..), as laid out in the appropriate section of the AI pick list data files. Stamping all over the naval gunfire support formations will do weird things for the AI beach assaulter!.
An OOB designed for
human usage only can generally ignore most of the limits (and entirely ignore the AI pick list), but be prepared for some end user who never ever read your never-read-me to complain when he tries to use your human-only OOB as an AI opponent..
The simplest way to edit an OOB and leave the AI pick alone is to
leave any existing formation alone or to make sure that it remains the same sort of thing (a tank platoon say), but you can edit the detail (3 tanks instead of 4, or rearrange the infantry types in a rifle platoon or the make-up of a recce company perhaps). You could extend the availability dates for an existing formation (back or forward) but it
must still be available at the original date range for the AI pick to utilise it.
And finally - although you can swap the OOBS in and out with the oob swapper utility, the pick list is not swapped. It is a global game data item. Therefore any massive rework (
especially including edited AI pick lists) is probably best installed to a it's own entirely separate game instance, with the scenarios and campaigns cleared out & replaced with some that use your database only. The only alternative should you try to have these co-existing with the stock set is really to provide a zip of a) your edited pick and b} the stock pick and instruct the end users to remeber to unzip the appropriate one when swapping OOB sets as well in the never-read-me file. Unfortunately - you would probably need to issue a new "b" set on each game release as we will not be keeping the stock AI pickset in synch with any third-party efforts!. So, for a massive mod - I would suggest a separate game install of its own.
Cheers
Andy