So, I've been thinking recently about the Scyk.

Naked, it's basically a TIE Fighter with a Targeting Computer.
With a Mangler Cannon, it's basically a less mobile TIE Interceptor.

With a Heavy Laser Cannon, it's pretty near to being a Phantom without a Cloak

With an Ion Cannon, it's...???

Like, I'm looking at this and thinking "Well, it's like an Ion Cannon Turret Y-Wing", but less durable, far more maneuverable, capable at firing at long distance, and incapable of firing out-of-arc, but also far cheaper (19 points for the Scyk, and 23 for the Y).

Too many differences.
Is it like an Ion B? No, as even though you've solved the "In-Arc" issue, and it's closer to being even on mobility, the cost difference is heavier, and the Scyk is far less able to fire its primary (being a 2 shooter rather than a 3).

It looks like this combination doesn't have a parallel in the game yet. Is it effective?

Problem is you have to pay five points for that Ion Cannon. It's the reason you never see ordnance on Scyks: the cost of it is already too high and the Heavy upgrade comes at a two point tax. They could just about manage a Procket Swarm in Epic.

The Cartel Spacer with an ion cannon costs 19 points. If you want control you might as well go up to Syndicate Thug ICT at 23: it's much better at it.

Not everything should have a parallel. Otherwise we'd just have one faction

It honestly depends what else is in your list and what else you have points for in your list. I recently swapped N'dru with LW out of my current tournament list for a Cartel with an Ion, and since I have an ICT in the list as well, I've actually got some better utility towards ionizing Large ships. Ion Cannons are nice vs the large presence of low Agility ships (B-Wing, YTs, Deci), and being able to reach out to R3 with the cannon is nice, too. You can Ion a small ship from a long ways out.

Exactly. You have to think about what you want out of your list, and failedparachute nailed it. If you want to add a degree of control, I find the Ion Scyk is pretty great at it for a reasonable cost. The nice thing too is being able to ionize something from Range 3 and then usually follow up with a primary at Range 1 since the Scyk has such a good dial. I also really like the ion for use right after a K-Turn; I can put that 5-K to good use and I'm not quite as worried about an unmodified attack roll (especially against a B-Wing or Y-Wing, since I only need two hits rolled).

Hmm I can't believe I never really considered this. Seems like it could be a pretty interesting filler ship. I may have to give it a go

Thanks for the idea that I should have considered but never did!

Not everything should have a parallel. Otherwise we'd just have one faction

That's why I was drawn to what the ship can do that no other ship can.

The problem with Scyks is that they're so fragile they shred like paper. At that point, you may as well spend the extra 1 point to have a higher damage output with Manglers rather than trying to Ion-control with them. The Y-Wing is arguably better because it can use its Ion Cannon as a turret or in a double tap from the BTL title with the sacrifice of being able to shoot at range 3. TIEs are arguably better since they have a 1-hard turn and are cost effective at 12 points, so they're easily more Swarm-able than Scyks.

Whenever I set up Scyks, I usually ask myself, "if I can strap a cannon to a paper airplane, what cannon is the best?" HLC is too much of a points risk, Flechette is garbage, Autoblasters are still too expensive, Ions don't provide enough in return for points, so Manglers are cost-effective and have a good damage output. Their biggest downfall, Tansarii Vets are at PS 5 which isn't that great and having them at 17 points hinders your list building abilities, and Spacers are PS 2, which sucks because one of them will probably get toasted before it can use its Mangler/Ion.

They're not bad, they're just not super-ultra-mega-phantom-Wedge Antilles-good.

Just my $0.02 from the 15-16 games I used Scyks.

I say choose based on what you need. Any ship with low agility is going to suffer against an ion cannon. I don't remember, but I think the Scyk can take auto thrusters so if you find yourself against a turreted ship you can use ions to keep yourself well out of it's arc so that you get the full benefit of auto thrusters. You can also use it to keep B-wings from swiveling around and shooting you. As well as keeping bombers from getting good bomb drops off.

I don't remember, but I think the Scyk can take auto thrusters so if you find yourself against a turreted ship you can use ions to keep yourself well out of it's arc so that you get the full benefit of auto thrusters.

It cannot.

I ran a list with 2 sycks, 1 with ion and one with flèchette. Worked pretty well, but have ony flown it a couple of times

It could be a less durable Tie Defender, since Defenders were the Empires' Flying Ion Cannons Tier 3.