Worried about sneak attacks? MLRS and Flak turrets get bonuses against most things that are built for sneak attack raids. Build them near your command station instead of scattering them. Sniper turrets can cover an entire system and fire at stuff that's otherwise currently out of range of your other turrets. If you are willing to spend the science, you could spread MKIII grav turrets around your home command, and use the leftover MKIII grav's to protect the frontlines. Even after that you can use the MKIIs and leftover leftover MKIIIs to protect your ally's home command in the same way you have. MKIII gravs are well worth the science. Alternatively, you could unlock widow mines and line-place a barrier between the wormhole and your command station. Or you can do both
If you want warning then zoom in on your homeworld, go into ctrls > planet-specific, find "Alert When # Enemy Units Present" and set it to 1 (two if playing Fallen Spire).
Raptors won't be my first choice but they are very useable with autokite. Set autokite to 1000 then they make excellent skirmishers and will survive a
lot longer. Auto-kite at 1000 will help most anything survive longer. Especially since it doesn't sound like your buddies are using autokite...
If force fields are annoying, start building Plasma Siege Starships. They do very high damage even ignoring the splash or the ability to damage stuff under forcefields. If each of you built your full cap of 2 sieges each, then you'll be able to rip through forcefields, especially with the aid of a flagship. Having six of those things traveling together will also make short work of any starship or guardian-related problems. But be warned, they are squishy, so never send them out without fodder. I find frigates make good escorts - they have similar speed and attack range, and since both use artillery hulls the plasma siege is less likely to get singled out by a unit that's anti-artillery. Also keep them away from needler guard posts, attack those with bomber starships instead.
Alternatively, you could just leave the force fields + guard post there and build the command center there regardless. The garrison might attack you for popping the command station early, but even at this early stage of the game a ten-ship garrison isn't exactly threatening.
edit: also if the force fields are bugging you that much then build a full cap of sniper turrets and let them slowly chip apart the forcefields instead of wasting your time
