There are many options available. The best for you will depend on your patience, skill, resourcefulness, and time available.
If they bubble camp your outgate 24/7, and if they’re half competent, then you’re best to get somebody else to move that cargo (Black Frog for example, or a better resourced corp-mate).
If they are not so persistent then you could just watch them to find a time when they’re not actively camping. Pop a scout alt into the system, on a perch near the ingate, and see when they’re active.
A miasmos is not a fast align-warping ship, even when fit optimally for that purpose.
If I absolutely had to miasmos-haul it out I’d set the ship up for fast align-warp, with a cloak, and I’d carefully scout myself out using a covops frigate or bomber. I’d use the scout to burn a perch at each outgate in turn and then warp the hauler there, cloak it, and then send the scout to the next system … rinse and repeat. Of course you’d need to be prepared to wait, possibly for a longtime, if a system is occupied and potentially hostile. Unless you can count all the people in the system in ECs and Citadels you should assume there’s a ‘dictor waiting for your hauler to jump in.
If I had a choice I’d engage somebody with a jump freighter and get them to haul it out, even all the way to Jita.
As for Syndicate, there is only one gate directly to hisec from that region and it is not camped 24/7. This I know, because I camp it part of the time. There’s another route that gets you to hisec via a single lowsec system … that route tends to be quieter than the direct-to-hisec route.