It doesn't make sense to combine the spotter role and the bodyguard role in the same unit. A spotter is suppossed to range far from the artillery unit, while a bodyguard is suppossed to stay close to the artillery unit. The only situation when one unit can perform both functions at the same time is a bad one -- when an opponent is getting too close to the artillery unit. You don't want your standard operating procedure for an artillery unit to be based on a situation that puts your artillery at risk.
So I'd separate your spotter and bodyguard roles into two different sets of units, i.e., a spotter proto point and a bodyguard proto point. The best spotter proto is probably the Satyr 4 with 6/9 speed, Light TAG, and AP Gauss. A Satyr 4 point will put five spotters into the field for you. The best bodyguard proto is probably the old Minotaur with 3/5/3 speed and dual ER Medium Lasers. A point could put ten ER Medium Lasers into an opponent that gets too close. (Against fast-moving opponents, the five Pulse Medium Lasers on a point of Delphynes or Gorgon 2s may be better.)
That said, personally, I'd stay away from mechs and protos in artillery units. Mechs are too survivable to be relegated to duty behind lines, and none available to the Clans except the insanely expensive Naga can throw two Arrow IVs per turn. Protos, at least the ones (one?) with TAG, are slower than vehicles for spotter duty, and lack the firepower or physicality of mechs or battle armor for bodyguard duty.
To maximize the number of units available to me, I like to use a vehicle/battle armor nova for Clan artillery units. Since vehicle points consist of two vehicles, I can pair an artillery vehicle with a spotter vehicle in a single point, while the nova battle armor point provides security for the artillery vehicle.
I prefer the Huitzilopochtli AAA for the artillery vehicle. Five Hueys can throw ten Arrow IV missiles downrange while protecting themselves with ten HAG-20s.
There's lots of fast, TAG-equipped choices for the spotter vehicle: Asshur Artillery Spotter, Donar Assault Helicopter (Recon Variant), Odin Scout Tank (Spotter Variant), Balac Strike VTOL (Spotter Variant), Epona A, Epona C, Hephaestus Prime, Hephaestus Jump Tank, etc. (The Epona and Hephaestus omnitanks, although munchy for their firepower or accuracy alone, are especially nice since the nova battle armor points can ride them onto the field.)
The battle armor points are a static but mean picket/speed bump intended to slow down or even fix an opponent to make them easy prey for the Hueys' ten HAG-20s. Elemental suits work well if you're comfortable with kneecapping and swarm attacks. Otherwise you want firepower, which means Coronas, Golems, etc. Given how slow they are, be careful how you spread out the battlesuit points. You want to make it hard for an opponent to penetrate the picket without getting kneecapped/swarmed or hit by a massive number of pulse medium lasers or SRM-6 packs (while also getting whacked by multiple HAG-20s).
Hope this helps.
