A few things...your team literally has no special attackers...the lanturn doesn't count with it being a wall and all...here's what I'd do. First off, any generic team is as follows: 1 special attacker, 1 physical attacker, 1 special wall, 1 physical wall. The other two Pokemon are up to you.
1) change your mega sceptile into a special attacker...giga drain/ leaf storm, d-pulse, focus blast and HP fire or rock....if it MUST be physical, then you want drain punch or EQ (maybe rock slide) not synthesis.
2) no amount of training will make an aggron fast. Unless you are running scarf jolly, it's not out-speeding Pokemon that are designed to be fast. It's just overall better to run max attack and max Hp with AV and 4 offensive moves if you want it to be an attacker or you can keep SR and the sitrus. The better choice would be to run aggron as a physical wall with max special defense and hp. I'd run SR, EQ, T-wave, and roar. If it REALLYwere up to me though, I'd drop this aggron because you already have steel coverage with scizor and that this aggron doesn't complement the other half of your core.
3) Scizor is also not fast. It's much better investing in bulk rather than speed. Plus, you already have priority in bullet punch already so speed isn't really an issue. I'd run max attack adamant with like 20 points in special defense and the rest in hp for a banded offensive scizor. As for the moveset, all the moves are good except double hit. That normal coverage doesn't provide you with anything significant. The much better choice would be superpower to catch steel type switch-ins like heatran. Something else you can consider is an assault vest so you can switch up your moves.
4) Talonflame is a physical attacker. Banded flame is one of the better offensive leads in the game as well. With your stat distribution, I'm assuming you want it to be an attacker. However, you have a support set that usually runs bulk. If running the bulky support set, you'll want to consider will-o-wisp, and roost. Tailwind can stay and brave bird is a must. If running and offensive set, definitely choose a physical variant. You can run band with flare blitz, brave bird, U-TURN and you can keep tailwind or go for steel wing or me-first. Also, always run gale wings. There's literally no reason not to...
5) the lanturn you have is perfect. By having it though, you are establishing a slow volt-turn core so the rest of the team has to work with it.
6) Mega rayquay is a big no-no in standard play so we won't talk about it.
Now then, there are a few things to consider. Your team as of now is extremely offensive. However, you don't have any wall-breakers besides t-flame (if physical band) or sceptile. Both of these are really frail so it's not good to rely on them too much. That's why you have to establish your core better. A core refers to the 2 defensive 'mons in your team. You have lanturn for a special wall, but where's your physical one? The only one that works is aggron, but aggron doesn't complement lanturn since it's weak to ground too and takes neutral from grass. You'll want a Pokemon that can cover lanturn' weaknesses and in turn have lanturn cover its weaknesses. One Pokemon that comes to mind is mandibuzz. It's immune to ground and resistant to grass while lanturn covers its electric and ice weaknesses. The only thing that will hit your core hard are rock moves. HOWEVER, mandibuzz can take a few super effective physical moves thanks to its amazing bulk. Fairies also hurt, but you have scizor for those things. You can run taunt, toxic, roost and foul play. Or you can also consider knock off and tailwind (instead of putting it on t-flame) Another very important move to consider is defog. If we do end up replacing mandibuzz for aggron, then you'll lose out on rocks. However, if you just change your tactic from setting up hazards to keeping hazards off the field, you should be fine. This benefits a offensive team like yours more anyways. As for the last slot, you suggested a gengar correct? Looking at gengar, it actually doesn't provide and coverage for your team. Ghost is immune to fighting and normal yet none of your Pokemon are weak to fighting. Furthermore, gengar is built to be fast and frail. You already have two Pokemon like that. For your last 'mon, I'd suggest a special tank. Something like a specs sylveon with hyper voice, hp fire, psyshock and shadow ball or an assault vest meloetta with hyper voice, shadow ball, psyshock and focus blast.