Create-your-civ game mode

I was wondering about a possible "game mode" where one would be able to choose their own civ's tech tree, bonuses and maybe even UU or UTs, and how it could be balanced.

My initial idea is that you'd have a certain amount of points to use and select or deselect certain techs. Removing techs (like halbs or paladins) would give you points to use, while adding them would deduct them. Removing pikemen (and thus halbs as well) would somewhat cripple you and thus give you more points for other things. This is pretty straightforward for normal techs but gets complicated for the rest.

Civ boni would probably have to be restricted in some way. Either being able to choose the percentages or just from the existing ones might not be enough. A civ with two or three early game eco boni could be really OP, so maybe restricting or increasing the next bonus' cost depending on what you chose already would make sense. Restricting it to one per "category" might also work.

Naval stuff presents a problem in that you could just go all-out on land units and be way more powerful than a slightly more balanced civ. However, a minimum for naval techs could be used, or the simply that you would be making this civ beforehand (and thus choose it depending on the map) could balance it out.

Architecture is irrelevant but I guess you could simply choose it along with unit language.

The idea here is that one could create very different combinations depending on the playstyle you're going for, while your opponent would be doing that as well. You could have really good cavalry and archers, including relevant UTs or civ bonus, but sacrifice eco boni, siege, and/or other aspects of the tech tree to balance it out. Or the exact opposite. You could also have more balanced or naval builds for different maps, maybe even for open vs closed maps.

This is probably easy to manually do as a mod for a specific tournament, for example, but how would you feel about this kind of game mode in the game itself? Would it become dominated by specific builds? Keep in mind that you wouldn't know what your opponent has until the game starts, and even then you'd have to look at their tech tree.

Can you think of some kind of trollish combos?