DISCLAIMER: I might take a couple ideas from other commenters to give their idea more limelight to the developer.
Name: Consuction PDA
SENTRY
Stat 1(Positive): Can Stick to walls and ceilings.
Stat 2(Posotive): Sappers have a low chance of "Falling off" and are deleted.
Stat 3(Positive): Makes Less noise than regular sentry.
Stat 4(Negative): Costs all 200 metal.
Stat 5(Negative): Can only be upgraded to level 2.
Level 1 sentry looks like workshop image.
Level 2 sentry has second gun and is smaller than default level 2 sentry, but shoots slower.
DISPENSER
Stat 1(Positive): Can stick to walls and ceilings.
Stat 2(Positive): Sappers have a low chance of "Falling off" and are deleted.
Stat 3(Positive): Fills up quicker than default dispenser.
Stat 4(Negative): Heals slower than default dispenser.
Dispenser fills 5 seconds before a default would, and metal ♥♥♥♥♥♥ from one load is 10 less than default dispenser.
Model would be created by developer.
TELEPORTER
Default teleporters only. To complicated to develop.
Just my opinions, I do really want a new PDA though. I agree, regular sentries are pretty boring.