A lot is simply based on the situation. You can have a formula, but an SL needs to be just as flexible as his SMs, probably even more so.

Assault

Rifle : Whatever you like really, I'm not going to tell you to use the Baur if you're a Voss lover, just use whatever gets you kills, and remember, all of the assault rifles can kill at all ranges. Does not matter what range you know you are going to be at most of the time, as long as you can use the assault rile that you choose, you'll always be fine.

Equipment : Defib, 100% necessary for any assault, especially SL. AR Rcokets as well, unless you are going to be at short range and you are effective with the shotgun. Smoke and radar grenade can be used in very special circumstances.

SL Equipment : Again, situational. I would never recommend the gun drone, but that's my personal choice, others may find it useful. If I am going to have a liability floating over my head, it should be effective. Gun drones do tiny amounts of damage, but recon drones can reveal a huge amount of enemies. If you're moving as a pack, the recon drone will just keep revealing enemies all the way to your objectives, allowing you to get a head start on any squad/lone-wolf approaching. Obviously though, beacons have, and always will be, a great asset to any squad. Again though, If you're moving as a pack,you should be able to keep each other alive by reviving, and you wouldn't necessarily need to respawn on your SL, unless your whole squad was wiped out anyway.

Support

Primary weapon : If you know you're going to be close quarters, then go Clark (unless you're like me and JUST CANT USE THE DAMN THING!!!!) Otherwise, if you're going to be a supporting SL, then you need one of the MGs, whichever you prefer.

Equipment : Whatever you like. On a map with lots of armour, obviously EMP nades, but evn then, they can be useful. IDS's and pulse meters can be useful as well. Sentry guns can also be decent. Either an IDS or a pulse meter is almost definitely needed, unless it's a huge armour map like HT, but even then, they can still be useful enough to be used ahead of the sentry and the IPS. Very much about situation, and what the SL is comfortable and experienced with using.

SL equipment : Well if I'm asking you to always bring either your IDS or your Pulse meter, it shows you how crazy I am about identifying enemies, and so I'm going to suggest the recon drone, although, if you have the recon drone, you don't necessarily need either of those pieces of equipment, especially the pulse meter, maybe there is still a case for the IDS. But at the same time, if you have a pulse meter, then you can switch to the beacon.

Engineer

Rocket launcher : Well if you're planning on fighting a lot of air vehicles, bring your SAAW, but otherwise bring your Pilum. However, again, just bring what you're comfortable with, and if you can use the Standard weapons better, go for it people.

Equipment : I haven't used the engy kit much at all, but I know what all of them do (except the NS unlocks). So I'll just give a guess, just for the purpose of getting a complete report. MMs are a given for pretty much all situations, and they are great for both offence and defence on armour maps. Also, EMP mines are good on defence, while the defuser is good on attack to clear the way. Also, you can dot the occasional radar around if you think it will fit the situation.

SL equipment : Well, oif you're on an armour map, there's a chance it's big and people can get seperated, or that the squad has taken an APC/transport and adopted it as its child, so a beacon will be needed to get dead squaddies back to the SL (and possibly it's vehicle).

Recon

Three types of recon SLs.

Sniper SL

Sniper rifle : Whatever they are comfortable with. Preferably a Zeller on armour maps to clear out enemy traps for vehicles.

Equipment : Stabilizer if they need it. Then, either APMs/RDX, if the SL doesn't need a stabilizer, then they should use both APMs and RDX. If they are going to be very mobile all over a large map, setting up in different places, then camo may be appropriate, as well as the decoy. Situational. also, note that there will probably more than one sniper if the Sl is a sniper, so you should probably have all with camo if they are all going to be mobile, and then have some with APMs and some with RDX, and the SL can have what he wants. Some may also want sniper decoy or stabilizer instead.

SL Equipment : Recon drone usually, to spot enemies. Again, if it is a mobile sniper squad, then a beacon is probably required to bring the squad back together if they get seperated (maybe one or two will get seen and killed, or you may have to sacrifice some to let the SL escape, and then the sacrificed can get back to the SL after (only if the ticket bleed is worth completing the mission)).Beacon will also draw less attention than drone.

Spec ops/Back-Flag capture SL

Primary weapon : Usually Lambert Carbine, but if the SL is very skillful with a sniper rifle (more than the Lambert), then by all means, they can take one of them.

Equipment : Camo, obviously. Decoy would also be good, but not necessary. If it's a spec ops mission then obviously RDX as well, and they can be useful in back-flag capture anyway. APMs can have their place, but only if the SL really knows how to use them properly

SL Equipment : Beacon. But never deploy it. Tell SMs to hold spawn and then tell them spawn in when you are either on a flag, or in a good position (down to SL's judgement). Drones will give away position when camo is operating.

Assault-minded recon SL

Primary Weapon : Lambert, 9 times out of 10. Only if the person if like in the top 100 for snipers in the wrold should they use the sniper rifle. Should be able to use sniper at mid-range, and sometimes close-range (but your SMs may have you covered), better than they can use the Lambert.

Equipment : APMs and RDX. Maybe replace one with the stabilizer if needed, and will be more effective than the equipment it is replacing.

SL Equipment : Pretty much same as assault.


For pretty much everything, I haven't written that you should definitely have this or that, it will always mainly be down to situation, but I've tried to narrow the options, while still providing any other relevant ones.