Let's talk some more about that silly ship the Defiant.
 
The Defiant had a cloaking device and after the first two episodes that pesky Romulan officer mysteriously vanished, so they could use the cloaking device whenever they wanted to, even out of the Gamma Quadrant. They just gave the Defiant the cloak so the ubership could be even more uber. Ira Steven Behr just liked doing whatever he wanted to, and he wanted to show you how kewl his ship could be, because fuck the Federation and Gene's policy of not sneaking around. Federation ships not having cloaking devices is so lamesauce, isn't it? So the Defiant had to have a cloak, which the friendly Romulans were kind enough to hand over. Sure, that made sense. Sure the Romulans, who had just brutally tried to turn Geordi into an assassin, sure they'd hand over their cloak to the Federation. Because they needed the data from the Gamma Quadrant, and they couldn't just get it in their own cloaked ship. The Romulans didn't have any cloaked ships of their own to explore with. They just had to get the data from the Federation, for some reason. They had to give the Defiant the cloak. Sure, they're not paranoid or secretive or hostile at all. It all makes perfect sense. And that Romulan officer leaving after the first few episodes... she probably just had some vacation time saved up and had to leave. No need to take back the cloak, the Romulans love the Federation. It made total sense. Or maybe that Romulan officer was still around, but we just never ever saw her oncamera again. Maybe they just kept her hidden inside one of the Defiant's supply closets, and she just monitored the cloak from there. Why not? Don't worry about pesky little details like that. The important thing is, we gave the Defiant a cloaking device. Because Federations ships are lame without cloaks. It's just so darn boring. We gotta give em more, more, more. Spice things up. It doesn't matter that they aren't allowed to have cloaks by the Treaty of Algeron. That's stupid, man. Give em cloaks, so we'll be such a cool show. It's such a cool little ship, ain't it. It's got a cloak and ablative armor and phaser cannons and it's really small and fast and it doesn't afraid of anything.
 
In all seriousness now: It's like the US giving China an F-22 stealth fighter in order to gather intel on North Korea. Would we ever do that? No, hell no. And it's obvious why. Not to mention that the Romulans had just learned that the Federation was trying to develop phased cloak technology and break the Treaty of Algeron, in "Pegasus." Is this knowledge going to make the Romulans more favorable to handing over their own cloaking technology? Hmmm, let's think about this one. I think the answer here is no. And one Romulan officer being sufficient protection is laughable. Remember, these are Romulans... a deeply paranoid people who excel in cloak and dagger. The thought of one lone Romulan officer protecting the cloak would hardly help the Romulan High Command sleep at night. And after the introduction, even that one Romulan officer disappeared. Even that flimsy excuse was done away with.

The Romulans also wouldn't care about risking one of their ships in the Gamma Quadrant, as opposed to relying on the Defiant. They seem to place relatively little value on life. They sent a lone ship across the Neutral Zone to test their new cloak (Balance of Terror). They sent a lone scout ship across the Neutral Zone to scout Galorndon Core (The Enemy). They blew up a scout ship to trick the Federation into buying the story of a defector (The Defector). They sent Warbirds to intercept Tinman at maximum warp, causing serious damage to their warp drives (Tinman). They blew up their own transports that were about to invade Vulcan (Unification Pt 2). They sent Remans to fight as cannon fodder (Nemesis). The Romulans were perfectly fine with risking their own ships and lives, so I don't understand why they now felt like they had to rely on the Federation for help.
 
And guess what happened when the Defiant went through the wormhole with the cloaking device for the first time. Answer: It got boarded and captured and the entire crew were placed in some VR simulation. The Dominion could now just take the captured cloaking device and reverse engineer it, or develop counter measures. So the Romulans would've never handed it over to some soft Federation crew. If they'd sent their own ship in to scout the Dominion, they could've given them orders to self destruct in case they were about to be boarded. The Romulans had no control over the Defiant or its crew. So no, it made no sense to hand the Federation a cloak.