I would say that the drones should have a limit as to how many enemies it can be attached if it doesn't already. This attachment only applies damage reduction and not damage immunity, in this way the drone acts as a Trinity in some way.
Drones have increased health and shield. Drone does not destroy everything it is attached to as it seems to do now.
Drones should be bigger and have a small weak-point on its back that's not affected by punch-through, that allows it to be renders null at any level. (This favors invisibility frames with scoped weapons/sniper/ accuracy)
Add in health stations like in Defection and ammo stations like in Cetus
Drones drop cores that can be used in such health stations to ramp of the amount of HP gained for a frame (health stations has to come with a limit to revival)
For every drone killed add in special buffs like plus Armor (additive) to go with these new debuffs in reviving people. Or reward people for reviving with additive Armor or some damage reduction mechanism. Or add in a screen selection where one can choose what power to increase (like an increase to strength, armor, or primary damage/status and so fourth). The selection would obviously ensue a time of invulnerability and have a limit as to how much you can select of each increase due to possible exploitation.
Add new enemies in Arbitration from the new content added in game and for every faction in general, such as Fortuna enemies etc... add a little more Eximus/ Corrupted unit. Most use the Simulacrum against Corrupted enemies.
Just throw everything you have. A flying T-rex? Add it. A dolphin with legs? Add that too.
Introduce flying enemies like insects or insects that dig under the ground (in this way they will be immune to damage abilities) that will favor CC frames like Vauban or Hydriod. Maybe these insects (fairly large ones too) can heal the damage reduction drone.
Maybe add in mini Bosses (for every 20-30 min)
Maybe add in a enemie, a big bad boy, that also is affected by warframe buffs and what not- lets a a Rhino buffs the team but this big bad boy is in the range, he too will recieve the buff. GG, but this could favor CC frames, especially Nyx
Anyway, increase sprint speed of enemies?
Hmm, what about a portal like in ESO that takes you around the star chart every 5 minutes. Could introduce gas city and those new enemies quite well, I really want to look up in the game and find a spider staring down at me. I'm getting spooked thinking about it.
Right now, weapons like the Arca Plasmor are favored heavily due to the drones and frames with high survivalbility are favored. This creates less diversity due to other weapons/frames being less efficient. This is a design flaw, but it addresses too much to change/rework. Endgame, if this is the idea of Endgame, should inspire most of the content/stuff created in the game. Endgame shouldn't derail players in using some frames, or some weapons. So in a way, I would like to see more of game mode that can put CC/squishy frames on the board, along with other or most weapons and the new content you are creating for the game.
Normalize the duration spent in defence, survival and others that are impossible to gain rewards in under or equal to 5 minutes.
Add better rewards such as Riven mods or riven mod components. Adding riven mods to drop table themselves could possibly make it too easy to make plat. Maybe have it as a reward for 100-150 vitus essence. If such rewards are added don't normalize the time spent, it will be too easy to get.
Make riven mods craftable, with components coming from reaching a certain point in Arbitration. Or that a mini boss appears at a certain point (maybe an hour) in Arbitration that drops components (at a fairly low but high chance, like 15% or 20%).
How about adding a new system (only in Arbitration as rewards with timed rotations) where faction based weapons (only those that are not of tenno) can be changed with additive stats?
This would replace wraith/vanda invasions. It would be up to the player to wraithilze? or vandalize? the weapon. In a way it would be like the Zaw Guilding system but for Corpus and Grineer weaponry. Of course for some vitus essence, and maybe endo. This would be better becuase from my understanding, wraith are only obtained from invasions (with the expection of ignis) and at some point it would take many months to get wraith weapons? This would completely deny that from happening if thats how it works.