Absolutely beautiful, we need a new PDA & this is the perfect idea. But I have a few questions about the concept.
1: The Name.
The Defensive Engie Pack seems like it should be more of an Offensive Engie Pack. The shield generator can be used to greatly aid your team in a push; & even though dropping the bear traps in a flank can help stop pesky Scouts or Spies, it could be handy to drop the traps in open areas where the defending team will surely be walking. Tossing one down in a choke point could mean the difference between capturing a point or losing it.
2: The Generator.
It's fairly obvious how the bear trap works. You drop it, someone walks into it, & they get stuck for a few seconds while bleeding to death. Awesome. But the generator is a different story entirely. It confuses me how it should work, does it act as a dispenser to your team with a farther range or does it place the wrangler bubble around them, helping them take decreased damage? This isn't Overwatch where there are three different types of health(Although that's kind of cool), so making it overheal your entire team seems to be one of the more likely candidates for functionality.
3: The Existing Buildings.
Which buildings will these two replace? It seems like the generator should replace the dispenser, & maybe you should sacrifice the teleporters for the bear trap, & that leaves the sentry gun. Although, if you WERE using this on offense, those teleporters are one of your primary concerns to keep on top of. They're what are getting your team back into the fray, & them throwing bodies on top of the objective will help get the capture. Not having that teleporter may be the Achilles heel of this entire loadout, so maybe you should be able to sacrifice the sentry for two bear traps, allowing you to not have to worry about keeping a gun up.
Regardless of my ramblings, I would love to see this in game. You have my upvote/favourite, & I'd gladly tell Valve how much I want to see this.