This mod does a couple of things.

• It makes the cost of fully upgraded sentries, cost as much as fully upgraded jokes
• It gives sentries and the Left Tier 3 skill (Engineering) the same bonuses as Partners In Crime, which is the +10% movement speed and +30% health and It makes the tier 4 skill, give health regen, like Hostage Taker.
• But they DO NOT stack with each other. So, no stacking with Partners In Crime and Hostage Taker
• Gives (via skill investment) the ability to pickup broken sentries, and makes the sentries mark specials
• It notifies via message if a sentry died, or is out of Ammo

And it changes the skill tree like this:

T1 - Third Law
Basic (changed): Your sentry guns gain a protective shield. The cost of deploying a sentry gun is reduced by 10%
Aced (new): You can now pick up broken sentries, broken sentries will lose 50% of their current ammo

T2 Left - Sentry Targeting Package Renamed to Tower Defence Plus
Basic (improved): Your sentry guns gain a 100% increase in accuracy. You can now carry 1 extra sentry gun
Aced (improved): Your sentry guns rotation speed is increased by 150%. Your sentry guns also have 50% more ammunition. You can now carry an additional 2 extra sentry guns

T2 Right - Eco Sentry Renamed to Eco Sentry Plus
Basic (changed): Your sentry guns gain 150% increased health
Aced (new): Your sentry will mark any special enemy hit by it, marked special by your sentry will receive 10% more damage

T3 Left - Engineering Renamed to Advanced Engineering
Basic (improved): You can now select a less noisy version of the sentry guns, making them much less likely to be targeted by enemies. Having a sentry deployed and alive increases your movement speed by 10%.
Aced (improved): You can now toggle AP rounds on your sentry guns, lowering the rate of fire by 75%, but increasing the damage by 250% and allowing it to pierce through enemies and shields. Having a sentry deployed and alive increases your health by 30%.
Note: Does not stack with Partners In Crime basic or aced

T3 Right - Jack Of All Trades
Basic - Untouched
Aced - Untouched

T4 Tower Defense Renamed to Human-Machine Interface
Basic (new): Having a sentry deployed and alive makes you regenerate 1.5% health every 5 seconds.
Aced (new): Having a sentry deployed and alive makes you regenerate 4.5% health every 5 seconds.
Note: Does not stack with Hostage Taker basic or aced

Developer note: I did not test it much, but it should be stable, if not send me the crash logs and the mod list