Alright, some input then (that's my preferred level of involvement in most projects, at least at first - let me know if it's unhelpful and I'll stop).
- Does magic/the supernatural exist?
Yeeeeeeesssss? The Antillia myth is tied to a boat of demonic priests that settled on the island. I like that. I also want to give space for priestly types and paganistic religions. However, I think the preferable scope on abilities is small. No gods appearing. No magic automatic healing. No supernatural abilities that allow you to overwhelm your enemies. etc.
Thematically that sounds reasonable. One of the problems on L&L games has been that faith-based characters either lacked depth, purpose, a niche or all of the above; on paper they had things to do but in practice they were often caught in a limbo where they lacked both political and military clout but were burdened by IC limitations (say, not being able to marry) compared to other PCs.
In terms of game effects balancing supernatural powers is tricky. A common issue for example is some of them are simply more useful than others, so you get the type that conveys the better powers. Another is that the cost to getting them needs to be calibrated as well - you'll know which ones pretty early on if your demographic gets really obviously skewed; players are typically great at figuring out where the best bang for your buck is.
Speaking of, what are your plans for the power curve? How will advancement (XP?) work?
- Is the game primarily PvE or PvP?
I think a good game is an equal mix of both. In Antillia, I would like to create an environment where characters are naturally at odds, but circumstances keep factions working together and keep any one group from ever winning.
Sure, but how? Do you have plans or only the goal for now?
d10 system. I have some game systems sketched out in varying degrees of completeness, but I since I plan on bringing more people on board, nothing is 100% settled.
Okay. I'm typically not that interested in systems, I just wanted to see if you were adopting an existing RPG or running an original one.
You also mention conflict How do you plan to systematize it staying healthy, and losing being a rewarding experience?
As mentioned, I have some systems in mind that would really benefit from having someone work with me on them. However, the TLDR; is that I think you reward what you want to see, and so XP is tied to healthy conflict to some extent and especially to 'losing.' I think the more a character 'loses,' the more XP they should get. Ideally, this should serve the dual purpose of keeping dinosaurs from ruling the game and encouraging loss as positive thing. Although, of course, game atmosphere and proactive staffing is equally important in this area.
Alright, some thoughts here:
For starters you are quite right, you reward what you want to see (or you get what you reward, whether it's intentional or not). There are many ways to skin that cat, but my very early advice is to design a system that's not going to require staff supervision over handing out every reward. It's going to drive up the workload very rapidly and it's really boring as a persistent task; consider going with a "trust, and verify" approach instead so there's a record of these things to catch abuse after the fact, but allowing players the leeway of monitoring their own advancement.
Beats in nWoD 2.0 are interesting. That system does exactly what you suggest - it incentivizes trying and failing. I would still put that firmly in the 'trust and verify' category as well, since it's a lot of work and scales up very poorly otherwise.
Don't be afraid to stealbe inspired by successful implementations in other games either. For instance Arx's making it a rewarding experience to play with newbies (through @rs) is an excellent idea. KD had a good one too where you filed a weekly report detailing what significant advancements you've attempted IC in that time; that allows staff to keep an eye on what's happening on the grid by delegating monitoring - and making it voluntary - to the players themselves, but also (theoretically) rewards attempts to make actual progress. If you reported "well, I had great sex with Jane" that wouldn't count, and if staff eventually noticed it you'd get a finger-wag.
What are character archetypes you have in mind for this game? Are there factions and what kind? What's the political environment like in very broad terms?