It is quite easy to hack your rep, I suggest using a memory program such as TSearch, and do a search floating point search for the rep you want to change. The game stores to reputations in memory from -1.0 to 1.0, however the reps seem to always be between -0.89999967 and 0.89999967 (The only way I've got full green and red bars is to set it that way, never actually got it without cheating.)

Here is what you do, do a search in TSearch for a floating point number with the exact value of -0.9 (This will only work if somone hates really hates you, 1 bar from full red). Play around with the results until you find the address that contains that value. Now you've found your string of addresses that contain all your reputations, from here on it's easy. Every 4 bits will be a new address for a different reputation. You can find the list of reputations in intialworld.ini, in the correct order. Liberty Navy is the first one, so once you find that address you can set any reputation value to whatever you want.

If you need a more detailed explanation I'll give it, just don't feel like it right now You can find TSerch from any good game trainer site. You can really fool around with a lot of stuff, but don't worry because you can't cheat in Multiplayer this way, the server holds the values which is why I'm telling you how to do this. I'm not a very good programmer so I doubt I'll be able to make a trainer, it's a pain in the neck because of the DMA involved.

-cheers