I'm attempting the same challenge and have spent hours resetting on Angie, Crawli, and even that Rift Chandelure + Nancy gauntlet. Narcissa was by far the worst though, and the field effect changes that came with V13 made it worse for the reasons you described above. Not sure why there were so many field effect changes because they used to be closer to what you're asking for. Turning the volcano top field into an underwater field was a legit strategy that took a lot of setup (volcano into cave with dig, freeze it with blizzard then shatter the cave into water surface, then use dive). The AI's pokemon have max IVs and cheated in EVs with optimal movesets for their respective field, so changing the field was definitely a huge component in beating intense mode but now that changing fields has become much more restricted, the game is just becoming tedious. The field effects are one of Reborn and Rejuvenations biggest charms, so the fact that its become so much more restrictive since V13 has come out really sours the experience (for me at least). Other problems i've had so far is the AI sometimes being way too smart like knowing exactly when to use moves like sucker punch, and knowing not to waste a turn burning a pokemon that is holding a rawst berry or has the ability guts.
Also, since you've beaten V13 on intense can you give me any tips on how to beat Zetta and Geara on Valor mountain? Been stuck resetting against them all day.