If you garrison your tower with 3 Crossbowmen and 2 Villagers, the resultant attack value will be equivalent to a garrison of 5 Crossbowmen. The advantage is using fewer resources and having the ability to quickly send the 2 Villagers to the the task of repairing the Tower after damage, if needed.

Good find and share.
However, for a player like me, it would be more beneficial to use the villagers to gather either gold or wood that way I can create more crossbowmen. Although they are more expensive there is also a chance that your opponent can use some type of siege weapon to destroy the tower, villagers can only repair a little amount compared to the damage bonus siege weapons have toward buildings. Then when it's destroyed you're left with 3 crossbowmen and 2 villagers, which in comparison is weaker than 5 crossbowmen when in ground combat. But I do see your strategy in this.

I think that this generally makes no sense. If you are attacked you should use the soldiers in the battle because they make more damage if they are outside the tower. And if your army is outnumbered, the tower will be destroyed anyway no matter whether there is anyone inside In fact the best way garrisoning in towers can be used is to save villages during raids. And honestly speaking, towers are redundant for me - only waste of stone which can be used for town centers and castles... This is, of course, for multiplayer game.

Towers are nice wenn collecting stone or gold at new area's, to save the villagers wenn get raided.
Also my strat is send a monk with 4 villagers.
Convert the first and then hide in tower.
Send 1 villager to the siege weapon for confusing him works also if no inf involved.