Lockdown is built from the ground up with the intent for classes to have unique special abilities that empower certain playing styles over others. Everything since release has been balanced and tweaked under this established rule; the amount of damage things do, the amount of health everyone has, the time it takes to reload/comeback/pick up and refire/swing/place weapons, and so forth. Adding outside "weapons" that go beyond the scope of the gamemode's original vision(Battle Sprites) into the classes active arsenals serves to only throw off the balance that has been precariously tweaked over the years. Suddenly players have much more firepower in their possession at any given time, but with nothing changed to compensate for the additional firepower. Even if things were changed in accordance with the additional firepower, it's still a ton of work to have to rebalance the entire game around the inclusion of secondary class-based abilities. This serves to overpower everyone. Now, you may be thinking that a game full of overpowered players is balanced--it's not;it just makes bad players die faster, and good players last a lot longer.

Simply put: it's not what the game was originally designed around, and professional developers like OOO should never resort to giving a cheap sense of short-lived "freshness" by destroying all the love and care that has made Lockdown endure with a gimmick clearly(from a balance standpoint) envisioned for PvE.

tl;dr BS are equivalent to lockdown armageddon

On topic: A new gamemode for Battle Sprites specifically would only work out if the Sprites were dropped to their lowest form for the match to preserve the wide range of competition that Spiral Knights' PvP is supposed to invite. There has to be something for everyone, and the fact that Battle Sprites can level up and change drastically would skew match results in favor to the team with the most hours clocked power leveling their Sprite. And even if you make it all balanced and such, there would have to be enough new content--other than having a different objective--to distinguish the new gamemode from Lockdown since the Battle Sprites themselves greatly resemble the Striker, Recon, and Guardian classes we already have. I can't foresee that being accomplished without adding new entities and rules to change up gameplay, and that's a lot of extra time the devs would need to put into a new PvP gamemode that people might not even play. Time they could be spending expanding the actual game instead.

tl;dr 2 much effort add t4 instead