I recently read a comment that argues that torps could get the inca treatment, lower build limit but higher pop space to account for their gathering effect and reduce their impact.
I want to maybe twist this idea a bit. Instead of capping the build limit at a lower level overall, torp build limit could increase with age up. Start at say 7 in age 1, 15 in age 2 then 20 in age 3( or maybe 7, 10,15,20 to add age 4 into this).
I think this will have 2 overall effect, it reduces the power of cards like blueberry in age 2 plays since there are less torps overall, and since it also introduces a cap in the pop space of swedes in age 2, there is a balancing act between just spamming caro or wanting more pop intensive units like mercs or cannons