i have been playing for a long time now, and the only planet i ever see faction swapping on (where 2 factions will appear in the level, and a middle period where both are in at once) is mercury. I think venus once or twice. that's really it. i actually really like the faction swapping concept, especially when dealing with corpus or grineer ship levels, as if an infested vessel has docked or slammed into the vessel and it actively invading.
i have suggested this into the warframe forums, if you like it, give it a like to make the idea more noticed or leave a comment there! Warframe Suggestion
the mission is sabotage. you must raid the grineer ship and destroy the reactor, crippling the vessel from within. but suddenly, halfway through the mission, there is a small cinematic (about 3 seconds, no matter where players are) where the camera would zoom out a bit, and the ship would shake violently, and it would end, with the lotus coming on and warning you about a compromised vessel boarding the ship, and that multiple bio signitures are flooding the ship.
For a little while, alarms will be sounding off, different then the regular alarms, and death sounds from grineer would be heard, along with gurgling groans from infested. eventually, after fighting through terrified hoards of grineer (running around aimlessly, yelling in their grineer language). freshly infected infested would begin to become the majority of the enemy type.
They would be the basic grineer lancers and sawmen, perhaps even a heavy unit if they are on that level, and they would be freshly infected with the virus, with the slimy hand latched around their bodies and into their faces, where the infestation is controlling them. they would be slower, and more noisy then usual, but able to utilize the weapons the grineer originally had, but with less accuracy and fire rates. (this would make sense, as grineer DNA is altered in a way which turns them into animal like beasts, unable to hold weapons, but before then they still have hands to use them). these enemies would only exist on these missions where the infested would board a grineer galleon, and no where else.
Note: since the regular infested were mentioned as being redone in the future since the ancients have, this would be the perfect opportunity to incorporate this idea, as this would mean regular infested on regular missions would be more then just lancer chargers, and instead some being grineer napalm units turned into chargers, so bigger and emit fire damage or something.
Scenario 2: you are on an infested mission. you must sabotage the asteroid base (or corpus ship's power core) against an infested-controlled mission. suddenly, alarms would sound, different from the ones in the level normally, as the lotus tells of an elite corpus/grineer vessel docking with the base/ship, she will tell you that "The grineer must have heard of our assault and has come to re-secure the mining machines before we destroy them" or "corpus scouts have alerted the Elite corpus vessels in the area, and have arrived to stop you from destroying the core of their ship and attempt to salvage it before you destroy it". the mission would then consist of elite corpus and elite crewmen coming in at waves, along with shield lancers (or shield ospreys if corpus), which will fight the infested in the general direction of the mining machines/power core, getting less infested the closer you get, and you will find groups of enemies guarding the objective.
i really love the dual-faction concept, and even making levels specifically for faction-swaps would really be fun, especially the infested attacking the vessel, which we never actually see. most infested seem at least old by tenno standards, as fresh infected flesh would be more shiny and stuff, in my opinion.
what do you think of my ideas? and do you think more faction swapping is a good idea? also, should i suggest this in the warframe forums as well?