NCA list design - new player

1. Not necessarily, but often. Both are mid-range attack pieces, but the Bulleteer can get much stronger odds against common targets and benefit from Hacker support while the Deva counters Smoke and Camo at longer range than a Rifle at a reasonable price. There are situations where you may want both and ones that you may not want either.
2. Fusilier Hackers are the cheapest source of Supportware in PanO, which can turn a Bulleteer or Sierra into a real menace. They also benefit from a Fireteam's Sixth Sense bonus to threaten hidden targets with Stealth. The HMG and Missile are usually fired from the DZ, the HMG can clear all but the toughest AROs with minimal risk and the Missile is a big threat-nobody wants to risk their Swiss equivalent against a missile outside of favourable situations, while rifle-carrying targets of opportunity like careless Warbands will likely not survive the Order. It's also a good combo with NCA's many TO AROs; anything facing down a Burst 2 ML and a TO MSR or ML at the same time is probably toast.
3. Doc and Machinist usefulness can vary. Doc isn't typically handy but can be a lifesaver if you're relying on a Swiss Guard to do all your shooting and eat a missile, and the Machinist is nearly mandatory if using a TAG due to the reliable healing and status clearing, and it's great if you're using Sierras too since it forces your opponents to spend orders taking them all the eay to dead. Bipandra or the Trauma Doc can also see a bit more use if you bring along the Bioimmune Bolts.
4. The ML Swiss is a dire threat in ARO due to showing up out of nowhere, letting you catch the enemy out of position, along with ARM 8 and -9 mod in cover making it insanely hard to take down. It also has a very accurate close-range shotgun, making it safer than the HMG from nearby enemy units, and is a menace to clustered troops with its many templates. If you trust your other troops to clear enemy AROs, it may be safe to leave the HMG behind and make the enemy suffer in their own turn using the ML.

 

I include a Trauma Doc with Palbot in every PanO list I build. PanO can't address problems in a passive way; we lack smoke grenades and White Noise that block hostile AROs, and virtually every maneuver we try to execute will involve exposing our units to hostile fire. Because of this, the Trauma Doc really helps you "try again" if a bad Crit or bad luck shows up.

That being said, you need to deploy a Doctor intelligently, use it well, and structure your list so that you have adequate Order Pools for performing these kinds of support roles. My lists are 15 Regular Orders minimum, which typically means I can spend ~2 or 3 Orders healing a key piece without feeling terribly taxed.

 

The Machinist on the other hand is rarely worth it for a single Sierra or Bulleteer. You're usually better off not running one in favor of another gunner that can be doctored.
Fusilier Hackers are a bit of a problematic topic in NCA.

1. You get one less basic Fusilier for Lt shell games. The difference in between 2 and 3 potential Lts on the board makes one heck of a difference. Both in people trying to go for it and in them succeeding.

2. Linking them exposes your other Link members to unopposed (TO) AROs and makes him the Link Leader. This means your Link can be broken by KHDs, Which is bad. Even if you find a reason to spend Orders on the Link to assign someone else as leader, the Hacker still opens up the Link to be reduced to 4 man boni by opposing Hackers. And everything is dangerous to you when you're WIP 12 and Hackable.
The other option is to not link the Hacker, which can force your Lt to join the Link or at least costs you the very important backup guy for your Link.

3. Your Hacking game will be pretty bad regardless or you will need to run Hexa/Deva on top anyway.

4. As mentioned above you might end up buying a Fusilier Hacker, Machinist and KHD for just one combat REM.

5. NCA is probably the most SWC starved Sectorial there is. You'll frequently want those 0.5 SWC elsewhere.

6. Attack REMs are terribly vulnerable. Being shit at dodging any sort of Template/Mine/Perimeter Weapon, vulnerable to Hacking, huge Silhouettes and no Prone State means they die a lot and fast. They're not a main strategy to rely on.

7. Buffing a REM every turn is a very basic strategy that always eats an Order to improve a very cheap attack piece.
PanO isn't really dependant on REMs to do work, you probably always have better gunners in the same list anyway - Swiss Guard/Aquila Guard/TAG. Running an expensive HI/TAG in turn means you want to run a KHD again to protect it.
Running the Fusilier Hacker effectively means you "lose" 2 Orders a turn. 1 to buff a REM that's probably in Group 2 and the second one because you won't be running full combined AVA5 on Fugazi+Mulebots - each costing the same as the Hacking Device. Opting for a different choice of attack piece, like a Deve/Hexa Spitfire or Garuda allows you more flexibility, uncrowds your DZ and generally supplements your Hackable main assault piece better, by adding an unhackable secodary gunner or an AD troop capable of circumventing a problematic Hacking Area.

There can still be good reasons to run both Fusilier Hacker and Machinist. Notably if you run a basic MHMG Squalo + Sierra.
Access to buffs, Exorcism and repairs is a lot of value. TAGs are expensive and both Bullteer and Sierra are pretty cost effective if you're short on points, as a TAG list usually is.

 

Of course, most NCA builds will include 3 Fugazi for orders and ARO duty.

Add a Bulleteer on top of that and suddenly there's plenty for a Machinist to play with.