Sounds good to me. With two choices at each level, you need to make sure that both choices are balanced. You also need to make sure that the player understands why one unit would be better than the other, but even then the differences can only be slight. A small shift in balance between two units becomes astronomical when you've got hundreds of them. Your skilled players will figure out which unit from each level is better and always use that, and crush new players with that knowledge. It's bad when most of the skill of a game is simply knowing which units are more imbalanced.
Now my real opinion is that I think you'd be best doing it with 3 choices at each level. At each choice level, the three new units would have a rock->paper->scissors relationship. The units would have to be mostly balanced with a small favor against one unit and small weakness against the other. This would accomplish a few things.
First, you're less likely to botch the balance so that there is only one good choice. If you've got two units and one just ends up being a little better, then that's always going to be the right choice. A R-P-S style would make it so that even if one unit is a little too good, it would still be weak against another specific unit.
Second, it offers a way for players who are behind to come back. The original evolves generally snowballed so that once you got a little ahead you couldn't be beaten (at least in 1v1). With a R-P-S style, the person who is behind now has a slight advantage (if they're good enough to figure it out). They can see what the other players have chosen for the next level and attempt to make a counter pick when they finally reach the next level themselves.
@arubaru304: Go
Sounds good to me. With two choices at each level, you need to make sure that both choices are balanced. You also need to make sure that the player understands why one unit would be better than the other, but even then the differences can only be slight. A small shift in balance between two units becomes astronomical when you've got hundreds of them. Your skilled players will figure out which unit from each level is better and always use that, and crush new players with that knowledge. It's bad when most of the skill of a game is simply knowing which units are more imbalanced.
Now my real opinion is that I think you'd be best doing it with 3 choices at each level. At each choice level, the three new units would have a rock->paper->scissors relationship. The units would have to be mostly balanced with a small favor against one unit and small weakness against the other. This would accomplish a few things.
First, you're less likely to botch the balance so that there is only one good choice. If you've got two units and one just ends up being a little better, then that's always going to be the right choice. A R-P-S style would make it so that even if one unit is a little too good, it would still be weak against another specific unit.
Second, it offers a way for players who are behind to come back. The original evolves generally snowballed so that once you got a little ahead you couldn't be beaten (at least in 1v1). With a R-P-S style, the person who is behind now has a slight advantage (if they're good enough to figure it out). They can see what the other players have chosen for the next level and attempt to make a counter pick when they finally reach the next level themselves.