Spies free after Flemish Revolution?

Would it be balanced if spies was free after flemish revolution was researched (free for the other player I mean, obviously).

Currently the militia count as a villager for the purposes of the spies cost calculation. But should they?

Feels a bit like fighting fire with fire, but if there's an incredibly strong short term bonus for one player, maybe it could be balanced with another very strong but permanent bonus for the other player (assuming they remember to click it when it's free) which would force the Burgundian player to make sure that they will win the game with the flemish push.