This is awesome. Indentured slaves, made to order, wedged between robot and man. And the idea of talking to a branded Coca-Cola man is pretty good, too. Great flavor. You've left me to speculate on their psychology, though. (What do they do for fun?)
A couple of thoughts. If they all must be paid enough to have a fair chance of buying off their contracts, the 4yr synths must make a good amount more than the 40yr synths (10x the discretionary income).
Second, the Dolly Effect sounds like the short lifespans that somatic cell clones have. These are caused by epigenetic effects (activating/inactivated 'tags' on the genes) and telomere shortening. I can imagine both of those problems being solved in my lifetime (well, maybe not dynamic epigentic imprinting), but definitely before we have terraformed planets hundreds of years in the future. If you want something to kill your synths with, I'd go with cancer. Overactive telomerase is how cancer cells don't die of old age, and nearly everything that speeds up aging/growth can be teratogenic. There's a lot of thought that we evolved old age as a defense against cancer, actually (our own form of planned obsolescence). So yeah, cancer.
Hmm. I was thinking about smaller versions, actually. Little ones that float around forests, eating an apple, and then retreating to the atmosphere to slowly digest it. Or ones with long, nearly invisible tentacles that eat birds. Or maybe birds that nest only on adult blimp dragons, and clean it of parasites? Do blimp dragons get fleas?
I've seen a lot of flying jellyfish before, but armored is new. Do they land during heavy storms? Could you escape a band of orcs by riding a young one up, up, and away (after cutting its tethers)? Lastly, there must be some sort of food you can make out of these things. I just googled "horse recipes" and got ~50m hits. I'm thinking: dragon jerky. Like tough tofu, it needs seasoning, but when one of these things dies, it'd be a shame to waste it. Go to Comment
I'd throw in a ghost. Maybe a zombie squid. Maybe make the treasure cursed, and the pirates are begging you to take it. Maybe the captain can control the ship with his brain and makes it do all these crazy barrel rolls during the boss fight. Why should he care if he sinks it? He doesn't breathe anymore, and he can bring it back to the surface just as easily. Go to Comment
When running a new party, get around the question of plot density by having the first discovery to be a deck of fate, or whatever you call it. If you use a real deck, you should definitely stack it to have the desired outcome, which is to curse the party to attract weird things to happen and involve them. This should not be told to the players at the time, so that they won't just up and try to get themselves 'decursed'. Though quite why they would want to is beyond me.