[Imp]

A few points
Map scale is 50m a hex so 4 maps to cover Annonobon.

When you say 1,000 ORBAT assume refering men, so 100 10 man squads or about the same & some vehicles if 8 man squads. Need to assign vehicles a standard crew cost or its a nightmare or say squads are 1 point vehicles 1 or 2 above cost XXX.
Tying to standard point costs could be tricky as a 3 man APC can cost more than a 10 man squad.

Thats a big force are we splitting into several groups I assume yes 3 Co a group would about fit for 3 groups.

Airdrop only, no problems but Russians can bring some quite good stuff to the game they have a lot of airdrop stuff, should they be using Paras. Talking airlift though think even MBTs can join the party if have a landing strip, Marines would land them
French are already there no idea what not Lecrecs but assume some vehicles there.

Strategic movement some forces may be mobile as in transport though slowest guy is the determining factor. Also need to take R&R into account somehow. Stay still for R&R

Adding reiforcements other players to an existing battle would be a nightmare.

An option would be sides purchase & split forces accordingly into battle groups.
Say 3 Fighting groups & 1 Arty, all units move, detemine battles, player allocates arty to battles then they start. If wanted reinforcements they would have to be set then to.

Lot of book keeping here keeping track.

I think DDs idea of banging a few heads together & coming up with a strategic thing that works is a good thing, keep it simple till hammer out & test. 2 sides say 3 forces each controlled by a player. Team decides strategic movement & Commander carries it out.
Examples arty assigning as said
Recon
R&R stationary? repair only if not in a base say. If attacked while doing can only use half your force to defend etc.
Doing on a grid is a good idea as maps flow into each other giving the feel of ebb & flow of battle as push across the map, also means need to do less maps.
Could try being slightly more ambitious slightly bigger grid say 7x7 possibly using something like TOAW to track units & there status (not thought through)
What constitutes a meeting or attack etc. Both moving, one stationary perhaps for 3 turns for dug in status.
If wanted to get clever could have 2 movement speeds column & battle formation which effect setup at battle start.
Time of day weather for vis, to incorporate this say 5 move phases (possible battles) a day 3 daytime, 1 night, 1 dusk/dawn. R&R can only be conducted every XX move phases & takes XX move phases to do.
Blah blah.

Like I said not easy folded my project early on once started thinking it through but a few people putting there heads together might pull it off. Then its a case of making maps. Say 100x100 with the borders containing 15 hexes from adjacent maps for continuity & to speed up making.

Also a simple system for book keeping needs to be sorted possibly spliting force into elements Inf/Armour/Support. For squads you would look at men lost & deduct that many from the next battle rounding to the nearest whole squad, 1 squad only can split to become 2 scouts etc. Damaged simple vehicles back in play after 2 move phases tanks more. Replacements? Alloted at certain times designers discretion.
A spreadsheet set up with some formula could then run it.

While think of repair could follow a points system. Each side gets a repair pool which could be reduced if they are attacked. Diffrent vehicle types cost diffrent amounts to fix from basic easy APC SPgun to MBT mobile AA hard.
If you have spare repair points you can spend double to fix them quicker. Gives the option to fix everything or rush the important stuff back to the front. Resupply is seperate & going into levels of damage probably to complex.