Anyone? How do I make existing units available to other units?

When I checked TWC a few seconds ago the patch .exe was still there. Are you sure it was taken down?

You should be able to make other units available to other factions in the ownership section of unit in the export_descr_unit.txt file. Looks like the building requirement is in export_descr_buildings.txt. Probably would be best to check in the modders Dungeon.

Taken from another thread about cheat codes (see the Oliphaunt reference):

NOTE: These are the main codes for Rome: Total War that are usually applied by typing text in-game, or by bringing down the game console. Please find the instructions on how to use these cheats below. Press [~] during game play to display the console window. Then, enter one of the following codes to activate the corresponding cheat function:

gamestop or bestbuy - 10% cheaper units in campaign mode
oliphaunt - 40% bigger elephants in campaign mode
jericho - Walls fall down in siege in battle map mode
list_traits - Lists all traits
date - Changes date
toggle_fow - Toggle fog of war
add_money 20000 - Increase money by 20,000 *
add_population - Add population to indicated city
auto_win - Attacker or defender automatically wins next auto resolved battle
give_trait - Give character the trait at indicated level
give_trait_points - Give points for indicated character's trait
process_cq - Complete all building in construction queue *
process_rc - Complete all military units in recruitment queue *
move_character - Move indicated character to desired coordinates
force_diplomacy - Force opponent to accept diplomatic proposal
invulnerable_general - General invincibile in combat
kill_character - Kill indicated character
season - Change season
capture_settlement - Capture indicated city
create_unit - Creates a unit in the selected settlement or characters army with the stats you input

* This cheat can only be done on a campaign map once per game. After the first time, you must save, quit, and restart the game to use it again.