This is a good idea to encourage players and build the community

...
...BUT, since Glest is an open source game it is very easy for players to cheat. There are no centralized servers or army of GMs and anyone can look at and hack the source code. Even with observers there is no way to know for sure that a player is not cheating in some way.
Under the current set up players play for fun and don't worry about cheating since we are a small community and most regular players know each other. Adding rankings will divide the community as accusations of cheating will surely follow with no way to prove or disprove them.
Lets just keep Glest as a fun hobby, there are plenty of other competitive games out there for people who want to get serious!