Wormholes

How we do it - wait for a quiet route out into hisec. Use orcas or several Itty V runs to drag fuel blocks from a trade hub to a station near the WH chain's hisec exit. Move it in from there either in Itty V's (if the route is short and very quiet) or DSTs. If the route is dodgy enough that you'd want to use blockade runners, it's not worth the hassle running POS fuel in unless things have gone very wrong and a POS is about to run right out (and avoiding this is why you should always keep a month+ of fuel in the hole).

Agree on that one, and occasionally you hit that system where the ice products are way cheaper then a trade-hub or is the cost of home-made blocks tons cheaper then a trade-hub.

It's also how you plan the import of all above mentioned. Either all in one go or bits per day/week.

It's less $$$ you're hauling through hisec.

As you say it really depends on the WH. It also depends on who is living in the WH and what skills the people have to work with.
For my corp, which is small and mostly new people it is way more efficient to make blocks in house. Even without full PI skills we have enough people to supply enough PI mats for the fuel we need and still do their own thing to sell on the market.
Our main industry people stay in the WH mostly full time so to make the blocks outside would mean travelling out. We tried it it's a logistical hassle to coordinate everyones PI mats and ship it out enough to make a run worth it and then back in. In house means that people just dump the fuel mats into a hanger when they can and get paid by the corp. It's dead easy to just have our ice miners mine and just truck in the ice products whenever the entrance happens to be nearby their stock.

Yes we could just buy blocks but the way we've set things up is to have the corp supporting our players to make isk while helping the corp. With how things are now I mine ice for about 10-12 hours a month. I truck the products in about 2 times a month whenever the entrance is convenient and someone is available to scout which is hardly a hassle. Then the industry people just make fuel at their leisure. For us it's got to the point that we're easily making enough to fuel another POS. We've even trucked fuel blocks out to sell when we've had lots of extra. (Not now though with the changes coming up)

Setting up our supply chain was a bit of a hassle but now that it's up and running it's so easy that we barely think about it. People just go about their business and our mat stock is always full. Then it's just " Oh the fuel bay is half full?" Slap in a run of blocks, several hours later take a minute to transfer the blocks directly from the assembly array and you're done.

Easy peasy.

We could use a mass efficient hauler, the Orca isn't cutting it, and the whole back and forth with iterons' is annoying.

Something that can drag in about 80 to 100,000m3 and not completely mass the entire whole in 1 shot.

I would agree with that. But I don't recall that being suggested anywhere. For me, IF I got my PI going again, I wouldn't bother with POS fuel, but instead with a more profitable isk/m3 P3 material, haul it out, sell. Fill up with fuel blocks for the return trip.