But seriously it’ll take some trial and error. Load three 5k primarchs and plenty of people will hit guards. Load three 15k primarchs and people will hit the primarchs for glory. In both cases players would search out your castle for easy sniping for glory.
Now if you have a t4 or t5 with a 100b marshal base, maybe 2k trappers works still because you can kill most attackers defending the guard/marshal base. If you have a t2 or t3 castle but have those same 100b base players, maybe having your 100b base player load an 80k trapper is best because again you can kill the attacker defending that base.
For teams who don’t have a very strong player relative to your rank, you’re in a tough spot. I’m guessing we will see 6-8k primarchs like we do now on accessible castles owned by normal teams. 8k primarchs would require 25k to hit guards which means there’s a good amount of their troops left to wipe out after one guard hit. You’ll just be forced to bleed guards to avoid bubbling often or accept you’ll leave shields on and take a bubble and overtax your leadership and players running cooldowns all the time until they say they’ve had enough and having castles (or playing the game entirely) isn’t worth it.