Still, it's been quite entertaining, if a little fraught. I started on Nauvis, rushed solar panels, and ran a low-pollution base until I used up the starting ore patches. I also set up my second base on a nearby island. If I'd studied the map properly I would have set up on the second island immediately, but we get there eventually. On the first island I set up my spaceport all ready to leave and built a space platform. I then realised I need to research a destination planet. This required some emergency sneaky ninja-mining at the marked 2.6M copper patch, surrounded by enemies.
Eventually I got off-planet, and moved to Fulgora. I built a basic base there, researched Vulkanus, and travelled there, where I built my main base. After extensive researching and some ninja-mining of Tungsten, I managed to kill a small demolisher, and then two more. This is the core of my factory, which runs nicely enough, but I obviously do need to spend some effort getting plastic production up. I also got Fulgora running nicely, but the bulk of research packs are made on Vulkanus.
Finally I got to gleba. The default deathworld settings affect only Nauvis, but I made sure to bump Gleba up as well, because why would you not. I built a base in the centre of a lake, then set up fruit producing spots nearby. This was before I had the jetpack, but by the time I got into proper fights, I did have rare mech armor, so could take on anything I met. The farms I sew the seeds on manually, then harvest with bots. Which means I do have to be on gleba to do, but I thought it would be ok.
Finally, I decided I should return to Nauvus. I wasn't sure I was going to do this, but the research buffs from biolabs are really super good, and this is Marathon, so all research costs 4x more. But biolabs do require uranium, and while I'm mining uranium, I would like to get a portable fission reactor instead of these portable solar panels. In any case, I moved from the first to the second islands, set up a flamethrower turret covering the edge of that mainland peninsula, using fuel from Fulgora. After a hard slog, I managed to take over the area in that first screenshot. And now, to the problem. I left Nauvus to set up Vulkanus to ship research packs to Nauvus, and while I was away, a behemoth worm set up nearby and started blasting my wall. I managed to move my wall defences back a bit to still be effectice but out of range, with only superficial losses. Still, I have no manufacturing on Nauvis at all, apart from sulphuric acid and rocket fuel. I have a single oil well, and the uranium patch, although I can easily take over more oil wells. I had planned to take over those nearby copper, iron, and stone patches, but they're not that nearby, and defending a wall that long really seems like a chore.
I had a couple of thoughts regarding behemoth worms. I considered laying train tracks around that 48 tile range, and running a rocket tank at permanent full speed through the surrounding areas. I'm not sure, but it's possible that the tracks themselves might prevent enemy bases from forming in those locations, although that may have been patched out.
The favoured solution is to place artillery, and manually target any worms. Or just let it run, I'm not sure. I do have 3 artys sitting in chests, but I need to import shells from Vulkanus. A more risky solution might be to allow enemy bases to form up until they're just out of range of the flamethrowers. There's an enemy base to the top left that's been there for a while, and any biters that spawn tend to burn to death before they can turn into worms. I could sit on Nauvis for a couple of days managing enemy bases and my defensive wall until they reach some sort of stasis. But I think I favour the arty approach. Except I want to keep that top left base to take over with a capture rocket. So careful positioning of arty to kill anything within 48 tiles of the wall, except for the top left base. Easy.
Really, I thought this was going to be difficult, and require micro-managing, I was even planning spidertrons which I could remote control to clear out enemies, but actually it can be automated, and I can farm on gleba without a care. You've been a great help

EDIT I had 3 rare arty on hand, but their range actually extends all the way to the iron patch up north. I built 3 vanilla arty to see what their range is, and started shipping shells from vulcanus. Vanilla range is still huge, you can see I haven't really used arty in the last couple of years. In any case, I suppose I'll plonk all 6 down, and slowly start clearing the local bases as shells get shipped in. I can even ship in more wall stuff until I do control a massive area, including the copper iron stone and coal. Or I can keep the current wall, and just let the arties run. The top left base was an early casualty, but assuming I can capture a base, the arties will leave it be long enough for me to build biolabs, and from there I'll re-asses.
EDIT EDIT
I reloaded with the top left base still ok, then placed 2 vanilla arty 31 tiles down from it, set to auto-fire. The other four arty I placed down set to only fire when targetted, and it's all going great. You can see the arty range is just about the full extent of this screenshot, and if I need more, I can switch to rare ones. I'll move the top wall up at some point, take over the NW base, and pipe in bio-stuff from gleba to keep it sweet. I'll decide whether to take over the copper and iron later. Currently I'm farming on gleba.