You have an RTS you rather enjoyed it.
It features 4 unique factions
Each one had there own campaign.
Had roughly 30 maps
Expansion would add:
Two factions with respected campaign.
8 Maps themed to the above factions
Releases maybe one or two a year
DLC would add:
A single faction with respected campaign.
3 themed maps
released roughly every other month or two
The example doesn't state what kind of multiplayer mode is included. If you want profit, you release an expansion with 1 or 2 factions, small respected campaigns. You use the campaign maps as multiplayer maps as well to save development resources.
Then you balance the new factions with the 4 old factions and patch the main program as well so owners of the main program can play against owners of the expansion in multiplayer mode. This way owners of the main program can get hooked on the expansion.
This got several advantages:
- You do not have to waste resources on several patches for the various addons, each requiring individual balancing but you can create one patch for both main program and expansion.
- Updating both main programm together with the Expansions and allowing owners to play against each other keeps even the main program fresh, on time and on high quality level. The High quality level and long time patch support done on par for main program and one or more expansions will prove the quality of general support for both the series and your company.
- Instead of splitting the community on several expansion not compatible with each other, you reactivate old owners of the main program when releasing the Expansion, even offering them new content to spend time and expirience on, together with the new players who will thankfully find players.
- You can even sell the Expansion as Stand-Alone. You would not need to own the main program. Owners of the expansion could host their 8 maps for owners of the main program to join, and owners of the main program could host their multiplayer-maps for owners of the expansion to join, though none of them could host the maps of the other game themselves, if they don't own it. This way you could accumulate all the maps created to be played online with every expansion.
The result would be a very active community, which might be rather essential for the success of a game or series.
What I clearly think of is Company of Heroes and its Expansions. CoH was released 2006 and received about 30 patches so far, from Version 1.0 to Version 2.6. The Expansions received less updates, I think the first expansion came with patch 1.8, the second expansion with patch 2.3. Until today there are still thousands of players online. You cannot state that for every RTS game. The whole concept is pure magic and I believe they got very great sales.