If you want a vision of Second Season, imagine a snotling stamping on a Bloater - forever
Gorge Not-well

What is a Nurgle?
Blood Bowl is a game about managing frustrations, and what team is more frustrating than Nurgle? Played right, your opponent burns through their rerolls while failing to deal with Foul Appearance, Tentacles prevent them dodging away to safety, and the passing game is ruined by the clouds of stink emanating from those Bloaters.

Team building philosophy
So in building a team, you want skills that will accentuate that: Guard makes the Bloaters harder to shift, and so does Stand Firm, so they should be prioritised over Mighty Blow and Claw. Bloaters don't need to get good, they need to get in the way. Maybe Tackle is a good third skill after Block and Guard, to deny Dodge rerolls, but equally some Prehensile Tail might be good to deal with higher AG sides.

Meanwhile, the Pestigors have the mobility and speed to be the hard hitters of the team; lower AV and a lack of Foul Appearance means they're more vulnerable than Bloaters, so they're slightly glass cannons, at least compared to the bigger lumps. So you probably want two of them, and as you can't be sure if you're meeting bash teams or dash, build one Block/Mighty Blow/Tackle and the other with Claw instead. Fourth score is either Juggernaut, so you don't get trapped if you run into a dwarf and roll Both Downs, or Frenzy, because, well, Frenzy is fun.

Rotspawn we won't mention, because the point of playing Nurgle is to strip reliability from your opponent. It's not to induce unreliability in your own team.

Seasons and compromises
In a perpetual league, there's no reason not to let Nurgle TV go up and up and up, but then they seem to converge to the same thing: four murderous Bloaters and then at least a brace of killer Pestigors, and my supposition is that Blood Bowl is meant to be about choices and living with compromise; a tricked out army of superstars avoids compromise, and so you're doing something different. That's not to disparage the high-TV teams, just to argue that I think I like operating at a lower TV. (I think it might be more fun to play against as well, but that's harder to determine)

Testing this out
But I wanted to kick the tires and see what this felt like, so at the start of January I opened the Gastro Pub, a Nurgle team that I planned to keep in the shallow end of the TV pool. I didn't want to make some min-max atrocity, but something that wouldn't make big sacrifices at season rebuy time.

It's not a perfect rendition of Second Season play: MVP allocation is still targeted, Tentacles will play differently and the jury is still out on Foul Appearance side effects, but I think it's about as close as I can get for the moment.

So far, it's been (mostly) fun. There have been some horrid games against Snotlings (at low TV they feel horribly OP against Nurgle, but again, Blood Bowl is about choices) but there aren't many nasty high ST teams at low TV, so it's been nice to avoid crowds of claw monstrosities. With my last Nurgle Box team I was running 180TV higher after 13 games (probably because I was choosing to run all available positionals and lots of Rotters, whereas now I'm keeping to an 11 man squad, three Pestigors, three Bloater build and not spending any of my treasury because I'm saving it for rebuy.

Future plans
After fifteen games, assuming no regen-less slaughters, I expect to have three Block Bloaters, of which two have Guard, and one gets an additional skill. I can't decide if that's Stand Firm, Tackle or Tentacles at this point, but I'm eschewing kill skills for the moment. The killer Pestigors only need Juggernaut now and they're done, Contemptible Cheese Platter is being groomed as the superstar of the team, and that's about it. One Rotter has Kick, there's no commitment to Dirty Player on the team, and then when we hit rebuy, we'll try to keep everyone, prioritizing Bloaters, then Pestigors, then Rotters. (If he lasts, the Kicker definitely gets sacked at the end of the second season because we don't want to pay a 40k premium when we can build another Kicker to replace him over the next season).

Over the long term, a lot of players may be too expensive to hold onto. This is a reason to not add skills to the Bloaters beyond their second, as they're good enough by then anyway. If Cheese Platter survives, I'm only taking stat ups from now on (prioritise MA, then AG, AV is silly and ST is expensive enough that I hope it discourages everyone else from taking it). If people think Second Season means less characterful teams, wait till you meet a MA8, AG4, Blodge Sure Hands Pestigor.

So, two matches until they go into hibernation ahead of the new era. I'm excited to see how it turns out. Also keen to see what flaws people can see in this strategy that I'm too close to this to see.