What Homebrew is possible?
 

I'm only just looking at HLO. (Been using PCGen for many years).
I see thta "most" of the Paizo material for Starfinder is covered as paid-for extensions (with some glaring gaps).
I also see a number of posts asking if specific aspects can be customised.
Can I instead as the more general question:

What, if anything, can be Homebrewed?

• Class - too complex, not expected
• Race - SF races arn't that complex, and often just recycle standard features
• Archetypes - like classes, I can live without
• Theme - also typically simple, with a boost here, and option there
• Background - just text?
• Equipment - level, cost, weight, description, (possible game effect)
• Weapons - specifically have damage type & size, specials, critical effect (standard list)
• Armour - weight, cost, level, KAC/EAC, expansion slots, special properties (from a list)
• Ammunition - bulk, cost, level, damage + type, specials (from std list)
• Spells - could be complicated, but many are no more than flavour text + casting time, range, duration, effect dice

Is there any "macro language" or formula system?

Or are we restricted wholly to what Lone Wolf have crafted and sold?

(Homebrew Race and Theme are top of my list as the campaign is starting, followed by equipment & spells.)

Kind of a mix on these, which we've been trying to expand some. There's no custom content entry like for HLC, due to everything being on a shared server, but we've added a number of options that can be added and customized. Races for instance you can add a custom race and add abilities to it, and with weapons/armor/equipment you can add custom items and set the stats. There's a limit to what can be customized on them, and to achieve stat modifications you also need to use adjustments on the character. I've had some thoughts on streamlining this that we'd like to explore in the future, but that depends when we can slot that in around other projects. We don't currently have a custom theme option, but that's probably something we can look into adding as a future enhancement. Might be possible with spells too.

could you not Key a custom item to the GM that created it, and let the GM share that item with their gaming group and no other?
It's a bit baffling why it should be shared with the whole world...

could you not Key a custom item to the GM that created it, and let the GM share that item with their gaming group and no other?
It's a bit baffling why it should be shared with the whole world...

They're not saying the custom item or class or whatever gets shared with the whole world. They're saying that their architecture has everyone operating on a shared system—the code on the server running HLO for you and delivering the web pages to you is the same code for everyone.

The concern is the possibility that some custom item, if allowed with the degree of scripting flexibility in HLC, might crash the actual application. In HLC, this crashed one program, HLC, running on your personal computer. In HLO, you'd crash the program for everyone who uses HLO.

It sounds like they'd have to make some significant changes to their underlying system architecture to allow this to happen. At least that's how I understand the explanations LWD has given.

That's a good summary from my understanding of it as well.

guess it was a really bad decision to design their system architecture the way they did then.

It's a trade off. I'm not an expert, so some of what I say may be nonsensical, but I do run teams of people who are and have worked on SaaS systems quite a bit. Multi-tenant architecture is easier and more cost-effective to scale. I've only seen elaborate custom scripting access in very expensive single-tenant SaaS applications (which doesn't mean other models don't exist, just that I haven't come across them).

I would guess they could turn these things into API calls, and then allow custom objects that only interact with the application via those APIs. But even if that was something that would work, it would be a lot of work that would take people away from other features and would probably not be as "easy" as creating custom user files in HLC.

I wonder if they could make custom items that are just collections of adjustments? The adjustments already exist, mostly. So I could equip a custom ring, for example, and it could give me a bonus to AC, apply an enhancement to my intelligence, and give me the ability to cast lightning bolt three times. I think most or all of those adjustments exist already—you just need to bake them into an item that I can equip and unequip. (And if Campaign Theater could let us transfer items between PCs and/or create a list, like a magic vendor, of standard and custom items players can acquire, we've got quite a bit of homebrew right there.)

Isn't this available?

I haven't used HLO in quite a while, but item sharing was near the top of their feature list in the early days.

I can't speak to architecture, as that's arcana outside my knowledge.

Spoilers, this is basically my thoughts on it. I'd like to see about setting up an adjustments table that can be turned on within items so the adjustments can be added directly to items, then have their activation tied to the item's equip state. Same with potentially Added Abilities and Spells. It's got a number of factors we'll have to work out I think, and not sure when, just tossing out that this is in line with my general thoughts at present.