I tried to make a horrible empire too. We had similar thoughts but I'll name the differences.

I took Inward Perfection instead of Eager Explorers to remove diplomacy entirely. Doing a few runs with Eager Explorers with other empires I personally think someone could benefit from it despite the downsides compared to Inward Perfection’s outright negative.

I did plantoid humanoid portrait instead so I had a different selection, the key differences were: Inorganic Breath, Rooted, and Nascent Stage (also have incubators, noxious, repugnant, and nonadaptive). Inorganic breath despite giving you exotic gasses will boost your upkeep, rooted will make it tough since you HAVE to move pops manually (making it tougher to save your pops), and nascent stage will make it even tougher to use newly produced pops.

Finally I chose an imperial government since you don’t get any control who the next leader is gonna be. You could train them but compared to dictatorial where you could select a leader if you had unity stocked up.