But if you tried leveling up to confront some rival Empire, or some Corporate super ship, or some monolithic AI, or some massive army, or some organized crime family with droids and sim drugs or whatever, even topping off your levels you are still likely to be completely unable to do any of these things unless the DM has carefully crafted a narrative where the world's resources are provided to your character so that they might temporarily borrow them and use them for some task the DM wants you to achieve.
This guy gets it. Yes, this ruleset pairs best with strong narrative control. In most fantasy games the players have massive freedoms and can do just about anything they want to, to anyone. Less so in fifth edition, more suicidal to slap the king here, but it is still there... this assumption that their characters own the world and can do anything. In Fifth Age I tried to create a setting that made the players feel like their characters were just people, heroic people perhaps, but still just people. In a world where a government, or mega corp, can muster hundreds of ships and millions of people, you can't just go around firebombing things where you are bored, or indiscriminately slaughtering customs officials. However the same comes true when you want to go take down the planetary dictator, or the corrupt ceo, or whoever, it has to be a coalition effort that the pcs are just hte figureheads or leaders of.
A lot of this comes back to just how deadly an interesting spaceship is in a world without ridiculous space magic. Any ship fast enough to be a good narrative device is a planet killer, and the characters will have to be held accountable by powers that be at every turn. Some find this constraining, I find it liberating to have actual authorities in a world, so the players act more reasonably.
As for the 10 level cap, it is very much by design to keep overall numbers down in the reasonable tier. HP caps at a theoretical 200ish for a marine with max con and feats, an average military npc that might menace the players at end game might do two attacks a round for about 16 damage per shot, and might hit half the time, meaning that a couple of squads of goons can reasonably kill the toughest character in the game in a single round.
Additionally, the level differentials in fifth edition carry over fairly well to here, I had a guy roll a first level character and tag along with a 6th level party, and he did just fine. Bullets were scary, so he kept his head down, but still contributed to fights, and was just as good out of combat as anyone.
As for Leveling after ten: I always liked el6 and had plans of letting my crew do that if it came up. My routine group has played perhaps 40 or 50 sessions, almost a solid year of weeklies, and just hit level 9 at the end of the last story arc. There are so many avenues to feel like progress is being made in fifth age that needing to "ding" is not such a big deal.
One of the things you will notice is that I dragged down the feat power levels by quite a bit, with feats like Sharpshooter being broken down into 2 feats, and the -5+10 bit being nowhere to be seen. I tried to make available feats equivalent to a +1 ability score bonus, so if you ever want to drag in feats from other sources and it is a feat that offers +1 ability and something else, just hack off the ability bonus and you should be fine. Ostensibly, I state that a DM can use feats from any source they want, and this remains true, just know that full on 5e feats might be a bit too powerful, so exercise your best judgement.
I will write more concrete rules on leveling after 10 in the future, but have no plans of adding more than 10 levels to any existing classes. 10 seems like plenty.
I am gratified to know that my rules are useful to people, and I promise further development is forthcoming, just a crazy time for me right now. I am always happy to log on here and see this thread in the first couple dozen.
Final note: Short barrel needs looking at, as well as close combat ranged rules in general, it is on my to-do list.