First tower :
Barb Wire - can be extended similar to what EV beams are in DD2 in a straight line only though, since it is a barb wire fence mobs walking through would take physical damage. It would be cool that when a prton beam or electric aura touches it the barb fence adds electric damage on top of the physical damage (would be cool to me at least)
Second Tower :
Claymore - it would be like placing 2 nodes, from dd2 on EV. first one would be the tripwire to trigger the explosive and the claymore could possibly be on a timer so after it's triggered mobs take time to get into the blast radius. for the range it would be like maybe a 75 degree arc (might be too wide i dont know) and range stat would only increase the distance of damage.
Third Tower :
Minigun Turret - im thinking minigun turret (does not target air units), this turret would also take on the property of the heros weapon damage type and heros weapon projectile type. probably cost extra DU for these bonuses because multiple projectiles can be OP.
Fourth Tower :
Rocket Turret - anti air only, AOE blast as well, im thinking maybe instead of rockets it can be a Flak Cannon so it would be a spread of explosions in the air - i think something like this would be awesome in dda since we dont yet have specific anti air only turret/tower/trap/aura.
im not sure about abilities but one ability could be a "repair/replenish" what this would do is act in a similar manner as monks dd1 ability that boosted and healed towers but instead it would heal and replenish auras/traps. of course it would not be instant and done over time and in a radius around the hero. Also the longer this ability would be active the more ability power it would use up depleting it quicker over time. Another addition is to have a secondary cooldown on the ability power spent so it doesnt reset with the main cooldown and therefore make it harder to spam. in invisible timer that gets reset over time.
for boost, the hero would take out a wrench and when you click on a single tower that towers stats get boosted for the duration with a long cooldown. this would increase all 4 tower stats so i wouldnt want this on a small cooldown to prevent it from being OP and abused.
thats my idea for this hero.