Dartling Gun was one of my favorite towers in BTD4 and BTD5, so I really hope it makes a comeback in BTD6. Anyways, here are my thoughts on upgrades for it (and monkey knowledge surrounding it). The Dartling Gun costs $810/$950/$1025/$1140. It shoots very fast, and each dart pops 1 bloon. It is a military class tower.
Powerful Darts, $520/$600/$650/$720 - Each dart pops 2 more bloons.
Barbed Darts, $595/$700/$755/$840 - Each dart pops 2 layers of bloon.
Laser Cannon, $5100/$6000/$6480/$7200 - Each dart can pop 10 bloons, as well as frozen bloons.
Ray Of Doom, $46750/$55000/$59400/$72000 - Fires a solid beam of laser with infinite pierce. Pops 1 layer of bloon per frame.
Ray of Boom, $85000/$100000/$108000/$120000 - The laser pops 2 layers of bloon each frame. Lead bloons and DDT's explode when popped, dealing extra damage.
Goggles, $215/$250/$270/$300 - Allows the Dartling Gun to hit camos and shoot 25% faster.
Bloontonium Darts, $850/$1000/$1080/$1200 - Allows the Dartling Gun to pop all bloon types.
Hydra Rocket Pods, $5950/$7000/$7560/$8400 - Shoots vicious little missiles with sharp tips that pop black bloons.
Bloon Area Denial System, $17000/$20000/$21600/$24000 - Shoots 3 missiles at once. Activated Ability: Bloon Area Denial System; Shoots out 100 missiles across the map, instantly popping anything below a MOAB and dealing heavy damage to MOAB class bloons.
MOAB Devastator, $42500/$50000/$54000/$60000 - Missles deal triple damage to MOAB class bloons. Activated Ability: MOAB Devastator; Shoots out 100 missiles across the map, instantly popping anything below a ZOMG, and deals extreme damage to ZOMG's and BAD's.
Focused Firing, $215/$250/$270/$300 - Reduces the spread of the gun from 23° to 8.5°.
Advanced Targeting, $425/$500/$540/$600 - Allows the Dartling Gun to target First, Last, Strong, Close, and Follow Touch.
Double Gun, $765/$900/$970/$1080 - Fires 2 darts at once.
Tag-Team, $2380/$2800/$3025/$4200 - Nearby Engineer Monkey sentries become mini Dartling Gun's that shoot very fast in a larger radius.
Gun Commander, $17000/$20000/$21600/$24000 - All Engineer Monkey sentries on the map become mini Dartling Gun's. All Dartling Gun's on the map have 25% more pierce and 10% increased firing rate.
Now for some Monkey Knowledge.
Deadly Darts - Dartling Gun darts can pop 1 more bloon.
Blinding Lights - Laser Cannon has a 5% chance to stun non-MOAB class bloons hit by it. Ray of Doom has a 10% chance to stun non-MOAB class bloons hit by it. Ray of Boom has a 15% chance to stun non-MOAB class bloons and a 5% chance to stun MOABs or DDTs.
Bloonchipper was a fun tower (though maybe not extremely effective) in BTD5, so here I am with upgrades for it in BTD6 (if it ever comes). It costs $640/$750/$810/$900 and is a support class tower.
Vacuum, $340/$400/$430/$480 - Sucks in bloons twice as fast.
Heavy Duty Blades, $380/$450/$485/$540 - Lead and Fortified bloons can be sucked in.
Sharp Suction, $680/$800/$865/$920 - Bloons are sucked in so violently they get popped an extra time.
Super Wide Funnel, $3825/$4500/$4860/$5400 - Super Wide Funnel allows the Bloonchipper to suck in twice as fast and suck MOAB class bloons (excluding the BAD) stalling them for a few seconds and dealing massive damage.
MOAB Slicer, $21250/$25000/$27000/$30000 - Super shard blades slice MOABS to shreds in mere seconds, stalling all bloons that come out for a few seconds.
High-Voltage Sucking, $340/$400/$430/$480 - Grants the Bloonchipper 25% more range.
Advanced Engineering, $510/$600/$650/$720 - Decreases the time it takes to shred bloons.
Triple Barrel, $3825/$4500/$4860/$5400 - Sucks in bloons 3x faster and shreds them 3x faster.
Super-Vac, $5100/$6000/$6480/$7200 - Sucks in all bloons (excluding BADS and DDTs (only if not visible)). MOAB class bloons are stunned for a few seconds before returning to where they were. Non-MOAB class bloons are kept until shredded.
World-Vac, $34000/$40000/$43200/$48000 - BFBs and below are instantly shredded, ZOMGs and BADS are heavily damaged.
Intense Sucking, $410/$480/$520/$575 - Shredded bloons are stunned for a second when released.
Advanced Programming, $850/$1000/$1080/$1200 - The Bloonchipper can detect and pop camo bloons.
Short Circuiting, $1275/$1500/$1620/$1800 - The Bloonchipper ocassionally short circuits, releasing a blast of electricity that races across bloons dealing lots of damage.
Chugging Chipper, $4760/$5600/$6050/$6720 - Allows the Bloonchipper to move across the map. New targeting options include; Follow Touch, Lock in Place, Patrol, and Pursuit. The Bloonchipper still has First, Last, Strong, and Close targeting priorities as well. Bloons run over by the Bloonchipper lose 1 layer per second.
Chipper Spewer, $42500/$50000/$54000/$60000 - Every 1000 bloons popped by the Bloonchipper releases a Mini-Chipper that starts at the end of the track and rushes to the beginning, dealing 1 layer of damage to every bloon it runs over every frame.
Now for some Monkey Knowledge.
Increased Suction - Bloonchippers have 10% faster suction speed.
Polished Steel - Bloonchippers cost 10% less.
Better Engines - Chugging Chippers, Chipper Spewers, and Mini-Chippers move 10% faster and pop 2 layers every frame when running bloons over.
You've got to consider the fact how useful this could be on 95 and 99, and especially freeplay(where DDT rushes are frequent). Also, 1 0 spacing DDT rush could do a lot of damage(even enough to take out the outer layer of a BAD thanks to the explosions. And if it's too Under-Powered, ya can just make all bloons or something have explosions.
A tower that costs $200k needs to be able to solo 80-99, and there's no way this actually beats 100. Only 0 spacing DDT rushes are on 263 where the DDTs now have over 50k HP, way too much for the Ray of Boom to take out by itself. With temples and such, this could still be useful.
How about Ray of Doom does 2 layers per frame (right now it's weaker than Glaive lord), and Ray of Boom does 5, with double damage to blimps?