I wouldnt even begin to know were to start making one of those
It's as F.B. said. A little more detail:
The following is the entire unitclass file for a modular unit.
Code:
[b]<?xml version="1.0"?>
<!-- edited with XMLSpy v2006 sp1 U (http://www.altova.com) by Derek Paxton (None) -->
<!-- edited with XMLSPY v2004 rel. 2 U (http://www.xmlspy.com) by Jesse Smith (Firaxis Games) -->
<!-- Sid Meier's Civilization 4 -->
<!-- Copyright Firaxis Games 2005 -->
<!-- -->
<!-- UnitClass Schema -->
<Civ4UnitClassInfos xmlns="x-schema:EWS_CIV4UnitSchema.xml">
<UnitClassInfos>[/b]
<UnitClassInfo>
<Type>UNITCLASS_GOO</Type>
<Description>TXT_KEY_UNIT_GOO</Description>
<iMaxGlobalInstances>-1</iMaxGlobalInstances>
<iMaxTeamInstances>-1</iMaxTeamInstances>
<iMaxPlayerInstances>4</iMaxPlayerInstances>
<iInstanceCostModifier>0</iInstanceCostModifier>
<DefaultUnit>UNIT_GOO</DefaultUnit>
</UnitClassInfo>
[b]</UnitClassInfos>
</Civ4UnitClassInfos>[/b]
It's the header and footer of the base "UnitClassInfos.xml" file (bolded) with the entry for the unit sandwiched between. There is one change that needs to be made to the first portion: You point it at a copy of the scheme file you re-name and include in the modular mod. Here it's "EWS_CIV4UnitSchema.xml".
I forget all the naming convention rules (Kael has a tutorial somewhere) - I always use "X_filename", where X is generally an acronym for the mod. Renaming is the only change you need to make to the schema files. And all your modular files should be renamed in the same fashion.
Text files: No schema needed.
You'd do the same thing for all the files. Header/footer with the entry for the unit, building, or whatever it is you've changed between. Even if you change only 1 thing about a unit, say, you still need the unit's whole entry. (There's a project working to change that, btw.)
Given that CivilizationInfos.xml can be a problem. To ban other civs from using a UU you'll often need to include the whole file. Other than that file, though, a modular mod is usually widely compatible with other mods and modules.
The only time you should need to update the module is when the schema files involved changed - and not always then. I think all the modules I made for FF 0.31 lasted until the BTS 3.17 patch.