The problem is it isn't that brief and its a fairly devastating imbalance..
Heavy Pikeman 13.5 vs Elephant Bombadier 16
Even the most specialized unit is almost 3 points down unless you completely rebuild your forces from scratch with Arquebusiers. But even then you still need one more tech, are one point down, have poor bonuses compared to the elephant bombadiers, and don't get to carry over your experienced units like the elephants can.
And it takes Matchlock, Metallurgy, Leadership, Calvary Tactics, and Flintlock until you can upgrade all of yours swordsman, pikemen, crossbowmen, macemen, etc. Five techs is not a short imbalance. Why can't all of those units just be able to upgrade to Arquebusier at Matchlock (preferred), or get a strength bonus at from Metallurgy (less preferred). The elephants would still maintain a good edge in both of these scenarios but not be completely overpowered for 30+ turns...