How about special units that you can build once you satisfy a requirement.

For example: If you were the first to research artillery then you can start building a Paris Gun. (You know the famous gun that bombarded Paris in World War1) It would be like a UU but anyone could get it.

Please post.

Flesh out your idea. Do you mean a simple renaming, or would this special unit have special characteristics?

I think ULTIMATEGP means that if you were the first civ to reserach a tech you could produce an alternative unit. There could be three ways:

1) The alternative unit could be a one off (like a world wonder). For thsi to work the unit would have to be pretty mean but would also have to have a weakness otherwise it could just stomp all across the map.

2) The alternative unit would replace the normal unit for the civ that researched the tech first. All other civs would build the normal unit. For example, whichever civ researches the techs needed for Modern Armour first can build M1s or T90s instead with a strength bonus or extra promotion whilst everybody else gets vanilla Modern Armour. This effectively gives you extra UUs and would definetly change the way people research to chase down certain AUs (Alternative Units).

3) The civ that reaserchs the tech first gets to build the alternative unit unit another civ reseraches the tech. Then they have to switch back to the original unit. Now I read this idea I think its a bit lame.

I mean 2 or 1. Both sound good.

Okay, I like the idea. The only problem is that the special types of units for earlier units are taken by Civ UUs. For examples, let's say spearman. The only special kind I can think of would be phalanx, and that's already greek. Or archers. I might be totally wrong, and I'm just so stupid when it comes to history I can't think of anything. Could you please help me?

It doesn't have to happen for every unit type. It could just be for a few that you can think of AUs for.
I think that 1 would be better than 2. 2 might easily be overpowering. Although, if it was a free promotion but you had to choose which promotion it was for the very first unit and then all others got that one, it would allow people to build armies/plan strategies to avoid you getting the best bonus from that promotion.

Perhaps you could also allow some of the promotions that the unit cannot normally take.

I don't mean every tech. I just mean a couple.

From a modders point of view idea one is easy to do. Idea 2 is possible but a lot harder to do.