I think testing swagger would end up coming down to what happened with testing sleep clause. In the end the issue became "was it fun to play" or not, and the choice was a simple matter of preference because obviously the metagame wasn't "broken".
Is swagger broken? of course not. Does it make for a less enjoyable/uncompetitive game? maybe
If we were to suspect test it the ladder would become absolutely horrible with the swagger flooding, but I still would support a test of the move swagger at any rate.
There is no way that Swagger should be banned. Using Swagger on a teammate holding a Lum Berry or Persism Berry is a legit strategy, with Swagger being used offensively against your opponent on the side. The latter part is luck-based but not the main purpose on Swagger and, more importantly, not too hard to deal with.
I'm also against banning SwagPlay/ParaSwag/ParaFlinch. They're all easier to handle in Doubles than with OU, as there are two Pokemon, and I have never felt that they were overwhelming or uncompetitive (well unless you build an entire team around it, but that team would suck). Banning them would hinder Pokemon like Togekiss unfairly. Remember that we unbanned sleep, which is a luck-based move based on the RNG, with a large consensus backing it up.
Regarding Mega Kang, it is the best Pokemon in the metagame in my opinion, and the Pokemon most deserving of a test. I don't want to state my opinion on it yet though. I'll play a bit of the devil's advocate here. Yes it deals a ton of damage but one thing that people forget to mention is that it has no spread moves (well it does but they don't get affected by Parental Bond), so other Pokemon like Mega Zard Y can easily dish out more net-damage in one turn, especially considering that Mega Kang is vulnerable to Intimidate. It's true that Mega Kang still deals a lot of damage to Intimidate users, but what if it hits the Steel-type or Ghost-type switch-in instead, particularly as the Intimidate user switches in for the other ally? And of course, Sucker Punch achieves nothing against a switch. It also has no resists to abuse for switching in, and Ghost-type offensively isn't that common, it's between common and uncommon - plus Mega Kang doesn't fair well against many Ghost-types.
Of course, this completely ignores that Mega Kang, in addition to power, also has great bulk both physically and specially, a hard-hitting Fake Out with decent speed to back it up, Sucker Punch, FuP for sweeping, and good type coverage (take 4MSS into account though). The Intimidate argument also works two ways; it makes Mega Kang's bulk stand out even more. Particularly when the only type hitting Mega Kang super-effective is vulnerable to Intimidate. For example, -1 LO Terrakion cannot OHKO Mega Kang, but after LO recoil, Mega Kang is very likely to OHKO with Drain Punch.
-1 252 Atk Life Orb Terrakion Close Combat vs. 252 HP / 0 Def Mega Kangaskhan: 338-400 (81.6 - 96.6%) -- guaranteed 2HKO
252+ Atk Parental Bond Mega Kangaskhan Drain Punch vs. 0 HP / 0 Def Terrakion: 288-339 (89.1 - 104.9%) -- 31.3% chance to OHKO
Regarding Zekrom, whilst I'm not entirely against suspecting it, I suspect it would be broken. Who cares if Landorus-T checks it when LO Bolt Strike + Dragon Claw hits so much of the metagame hard even at -1 Atk and it has the bulk to stand up to a lot. It also only really needs Bolt Strike, Dragon Claw and Protect to function on non-Choiced sets, so that other move could easily be something like Tailwind, which can also screw Landorus-T switch-ins with your partner, Outrage for intense power, HP Ice or Draco Meteor for Landorus-T, or even Imprison to screw over opposing Zekrom. And unlike Mega Kang, it has resists to give it switch-ins backed up with even better bulk and power, and the ability to change its item.
Also in case you think that Zekrom can be easily burnt:
252+ Atk Life Orb Teravolt Zekrom Bolt Strike vs. 252 HP / 0 Def Rotom-W: 320-376 (105.2 - 123.6%) -- guaranteed OHKO