Hi, i'm hoping you're having a pleasant day, that birds are flying above your head in a peaceful way... Because now, we get into business : 1rst imagine these birds get deny really hard by a fat russian character using the badass weapon of all time (even has to use the prefix "mini" so it seems not that dangerous) : The minigun.
To talk about that change, we could first the discuss about the strenghst and weaknesses of both classes,
Then what would be your usual heavy game in a 6's format according to the previous topic, and then
we will see what it brings to the 6's meta.
But before that, i'll explain how this thought came to my mind.
It may be common knowledge, I used to play pyro in 6's A LOT, a year ago.
Guess what, it worked pretty damn hard, and there's multiple reasons behind it :
1: A good theorycraft, which brang me to use, for example, to detonator instead of the casual Scorch shot, reasons, you have a more stable dmg output, [b]even if the ennemy is on the highgroun[/b]d, which makes all the difference, compared to the scorch shot.
2: a little amount of high/prem experience, to set foots into the class, and the get a basic understanding of how the class should be played.
3: Obvioulsy, the pyro update helped even tho the difference was not that huge, in term of flaming 1 man down.
(I'd like also to point out [b]that the pyro idea came before the update, and i was already starting to play it in scrims[/b])
4 : And this is my main point : you force the ennemy to [b]adapt[/b], which can be, for some players, the hardest thing they're able of.

After this quick introduction (lol), let me sum up strenghts and weaknesses of both soldier and heavy :
Soldier, with the pocket role, has a massive aoe dmg potential at close range, good spam ability (which normally means, that you can deal good damage from long range [b]if[/b] the ennemy doesn't see you well, or really want to take a certain position.
He has insane mobility with his rocket jumps, and has a good amount of health, which allows him to get in and out better than other characters.
This class is supposed to control closed area, and also engaging from above really fast and still manage to survive.
On the other hand, he has low ammo, low clip (that plays a lot in terms of constant dps, which he's not capable of)
he struggles to deny ennemies that are on the high ground, and sucks terribly at fighting scouts.

Heavy, is the king of mid range and close range, and has the bigger health in the game 300hp. He stands for the guy you don't want to fight alone, or even get close to him. he's the defensive force, and the intimidator of the game. He also has a constant dps, and a huge reserve of ammo in both is clip and ammo reserve (which are the same on heavy).
However, he's also the slowest class in the game 77% of the usual speed for example sniper, engineer, pyro and spy, and even slower when he fights, with a speed of 37%. that plays a lot when it comes to dm situations, where you do have the biggest hitbox and the slower speed, that makes him a really easy target for the opponents. He cannot chase because of it,

So as we've seen that point clear. we can speak about what will be our average game of heavy in 6's :
1- Rollout, [b]you have to equip "Gloves of Running Urgently"[/b] ! just do it, or you won't play the mid. When you strat the rollout, make sure you take the gloves in active, at the moment you're able to move, that would help when you arrive at mid. When you arrive, you'll have between 200 and 130 hp, which is going to regenerate with time.
Obvioulsy you know that because you're smart heavy main in 6's, you don't want to get burst at the entrance of the mid because of your low health, so instead what you can do, is playing on highground defensively, which would help you get your health back.
2- Position : Because you're slow, and easily focus-firable, you don't want to come close in a 6v6 situation, but you're not useless, if you get a good forback position, you can spray those 5-10 tick damage (on a non-healed target), to force them to do something, otherwise they just back, and you get a free capture point. This forback position, or even covering position was given to my mind, thanks to my lovely Kresnik, who inspired me for that point. Because indeed, this position allows you also to avoid your primary threat, that is not focus-firing, that is sniper. being forback and keeping sight of where you med is can allow you to take a cross fire angle, that would not allow the sniper to kill you easily. you can also deny the soldier jumping OBVIOUSLY.
what is from my own reflexion, is transition phase, where as a heavy, you might be surprised how weak you are when you're running, not spunning your minigun, at 300hp, many of the casual 6's (expect medic) can destroy 1o1 if they come close to you at the moment you're not expecting. to give the heavy a safe tool, i personaly use "Family Business" to get rid of the pesky classes that tries to get you in transition phase. this weapon has a higher dpm rate due to its clip and speed firing of 120%. Of course you don't the luxury of having a magnificient sandvich, to heal you or your teammates, but i found my self more useful with that weapon to protect your medic. also keep in mind that as heavy, you'll get wounded really really really often, so your medic can just get an advanced self-heal rate, just by keeping the beam on you, so that's win-win. Keep in mind also that getting a position as heavy, is the thing to do, no matter how low the scout behind was when he tries to escape, you're not fit for this job, your role is say " This point, this medic are now Russia" and defend it like it was your own motherland.
3- Coordination : You have to tell you teammates to keep in mind you're heavy, not a soldier. They can't go for an uber ad really deep behind the ennemy line, in general, any form of chase they have to be careful, because you'll be late to cover their back.

Conclusion part :
I think the heavy could be an interesting thing to try strat-wise, and fits extraordinary the safe teams, that could use an uber ad just to get control points, and also this kind of gameplay goes with the 4 part of my introduction : you force the ennemy team to adapt, since they're not aware of this kind of games.

That was all for me, i hope you're getting ideas to play that fat class this season with your team, and i'm waiting for the monkeys, who didn't even red the whole to say how much they hate me for having played a certain class in a videogame, from now on.