I made one out of a region of england. You can check it out and download the appropriate file here: Lincs & Humber Nation Database for FM12
Pretty simple process.
Guide to Creating a Regional Database
Last updated 06/12/2011
I am swapping into a custom nation from England for this example, it will leave England in a playable and relatively untouched state:
: Enable editing the continent in the editor (see here how
Replace a Defunct nation... C.I.S ore Pre-1922 Ireland are pretty good, overwrite one with your nations details and clear out anything that is not relevant. Set its continent to Europe! (see above link)
Identify which cities you want to include in your nation and change their nation
Idenfity all the people associated with those cities and change nationality to your nation (see posts later in this thread on who to include and who to exclude from those who are born in your nation)
Add a league in the competition tab, name it and set its nation to your nation and with the correct continent.
Add a the required number of English teams from "A lower league" (they will take on your nations nationality but dont worry about it).
: try just 6-8 teams to start with and filter out any from the "a lower division" with a "Next Division" and "Last Division" set.
In England identify the required teams, swap each time with a team from a lower league without a "Next Division" and "Last Division" set, if your identified team has one set manually change it to a team without one.
Continue this until all your teams are in a non playable league (below BSS/BSN on default database)
Swap the teams from your custom league into the non playable league, this will automatically correct the teams nationalities (handy isn't it
Europe only (as far as I know): Set all the spaces in the nations coefficient section to 0.20 (or 0.17), for more continental qualification places match your nations coefficients to a nation of the same level you want, if you get negative numbers for cup places in the game try different coefficients.
Add the national rules so your league is playable.
Test! - Note any potential changes or issues and revise
Repeat steps 4 AND 8 for the next league down, when adding custom teams there is no need to do step 8. Just set the nationality to your nation and the competition to your league.
When all your teams are in and all your leagues are done add some cups
Check all club relationships for possible feeder clubs in the same division as each other.
Test again! - Note any potential changes or issues and revise
add any extra details such as graphics, awards etc
Pop it up here for beta or release, depending on how the tests went
Always remember! Save often to a new file (1.00, 1.01, 1.02 etc), write down the major changes for each version and test frequently!