I could see the BMM and similar books as the following pattern:
* BMM - rules for fighting Battlemechs. DLC could include a few basic vehicles and infantry units for variety. This would be the core book, with simplified rules for other units (i.e. just listing the cost and effect of an ASF strafing/divebombing run, rather than the full cost/construction). I'd like to put the Mech variants in here (Mechs would be defined as a legged unit where the pilot is contained in a single location)
(future books)
* MechMakerM - making Battlemechs, including the construction rules, with a list of tactical items that can be put inside.
* VehM - rules for fighting and making Vehicles. For the engine charts and weapons to put in the vehicles, it refers to the BMM. Lots of sample vehicles are provided. Anything that cannot be included on Mechs but can be included in Vehs would be put in here.
* TrooperM - Infantry units, including power armor (where the pilot's body is in multiple parts of the suit - i.e. head and torso of a
Rottweiler). It would include rules for the various ground unit weaponry in both BattleMch and RPG scales. Lots of sample infantry units are provided
* AeroM - rules for fighting and making CF & ASF. This includes air to ground, ground to air, air to air, and battles in space. Construction would refer to the BMM for engine mas and weaponry/equipment. Anything that cannot be included on Mechs but can be included on CF or ASF would be put in here (and could duplicate parts of the VehM tech listing)
* SupVehM - fighting and constructing Support Vehicles and Buildings. This is where the 'strategic' items are included, such as MASH, Mobile HQ, Mobile HPG, etc. Sub-Capital and Capital weaponry could be listed in here to allow construction of ground-based orbital defenses.
* SpaceM - fighting and constructing Dropships, Jumpships, Space Stations (of which satellites would be a sub-group), and Warships. This is the key book that would have its own new set of rules, due to the lack of gravity and Newtonian movement. It would use the BMM for small weapons, and a copy of the SupVehM charts/data for strategic items, Sub-capital weaponry, and Capital weaponry so you don't have to buy the SupVehM.
* Index - Every key word is added to this index, so people can search for "Engine Chart" and it will have sub-options for Mech, Support Vehicle, and Starship, each with the book that the word occurs in and the chapter/heading to look for. If you see something interesting and you don't have that book, now you have a reason to research that book to decide if your interest is greater than the cost
Each of the books after the BMM would include the rules for that unit vs BattleMechs, and include how that unit is to be treated in its variation from a Mech. This way players only have to learn the BMM, to understand the basics.
For example, VTOLs being fired at by Aero would have the to-be-hit of a VTOL explained modified so the VTOL is treated as a Mech. From this, the Aero book can then use that modifier and roll as though it was attacking a Mech.
The goal should be that you buy the BMM as the core book, and all other books are 'attached' to it. The most modern rule overrides the older rule
Imagine if all of the above was in a single book or PDF. Fewer PDF are nice because you can search through fewer files, but some people might not want to buy all the components at once (or ever). A beginner player might just want the basic Mech combat rules, while the price of the Megabook would discourage purchase
(The other reason for using multiple PDF is that if one book is updated, you only have to download that single book, rather than the entire PDF)
Dude, that registers about as much as a whale fart in a submarine battle.
Unless you hear what sounds like two whales -
https://www.youtube.com/watch?v=OEpEv6kWdtw :D