This is actually something Tarkin did in both Canon and Legends, though with a variation of intents.
by lord Martiya

Year 4 of the Empire: Wilhuff Tarkin raises an army 2

"I admit I didn't expect it would be livable so soon." Tarkin stated in the currently main hangar bay of the DS-1 "Imperial Planetary Ore Extractor" (whoever had come up with that cover name deserved a raise, Tarkin decided). "You and your collaborators are surpassing my expectations."

"Why, thank you." Orson Krennic, director of "Project Stardust", replied, wondering what his superior in the "Tarkin Initiative" think tank and potential rival for the Emperor's favor was planning.

"I trust it'll be as unassailable as it's supposed to be once I'll take command."

"Wait, what? This is my achievement, not yours!"

Tarkin looked at the director, genuinely puzzled. He had expected more sense from him-but if nothing else such unrealistic expectations explained some of his attitude.

"Director, who is better in hitting a target with a DC-15 blaster, the designer or a trained soldier?" Tarkin asked.

"The soldier-hold on, is that what you're saying? How you'll take my credit?"

"This station is the most astonishing engineering feat in the known universe. The only artificial object that surpasses it in size is Centerpoint Station, and that one isn't mobile. History will remember you for designing it and for supervising the other aspects of this station, but I'm afraid that you're qualified to lead it into battle just as I am to design it."

"I-I see."

It wasn't what Tarkin had hoped for, but it was all he could realistically expect from the ambitious director. Once he calmed down he'd get around, he was an intelligent and normally sensible man.

"The only ways I'm qualified to help this project is making sure you receive what you need for the actual job and a few other measures, including the one that is disembarking from the troop transports right now."

Tarkin was referring to thousands of armed men, all carrying the standard DH-17 blaster carbine of the Naval regiments but otherwise looking much different. The Imperial Navy Infantry Corps uniform still consisted in the azure shirt, grey pants, black vest and boots, and white and black elongated helmets in use since the early days of the New Sith Wars and kept in use during the "Great Peace of the Republic" by many planetary defense forces and the Judicials' naval infantry before the Republic Navy and its infantry were restored, the only change being that they wore the Imperial Crest in a patch on their left sleeve while their predecessors had worn the Galactic Roundel. These men instead wore all-black pants, shirts, boots, gloves and helmets, the latter being of a design closer to the Imperial Army's helmet but enlarged. After they deployed in parade formation in front of the two commanders, Tarkin addessed them.

"Welcome to your new assignment." Tarkin said. "I'm sure you wonder what this assignment is, you've been taken from your units, assembled in brand-new ones, and made train together to properly form it, all without being told what you're supposed to do, and then brought to this immense station. The answer is simple: you are the best men of the Imperial Navy Infantry Corps, chosen for the skills at your job and unmatched ability to keep proper secrecy, among other things, and will guard this battlestation. Born from the union of an idea of Raith Sienar himself and a planned Separatist superweapon they thankfully lacked the ability to actually build, once completed the DS-1 Orbital Battlestation shall serve as a mobile naval base for the largest fleets and to break sieges by destroying planetary shields, with enough power to wipe out the planet under them if the threat is vile enough. And you, the Death Star Troopers, will guard it, both during construction and after completion. The whole galaxy trusts you."

And with that, another part of Tarkin's plan was in place. It would take time, but the crew would be entirely composed by people who'd put their duty to the people of the galaxy before the one to the Empire-and any exception would have to deal with them. Now, how he'd justify modifying their uniform to include some armor to take even on Stormtroopers, just in case?

notes

In both Canon and Legends the Death Star Troopers were the closest thing Tarkin had to a personal army, created specifically for the Death Star and so influential their uniform was eventually adopted by the whole Imperial Navy for their soldiers. Here, of course, they also have another job... Though they don't know that yet.