@vppreddell
If you want, you could use the mod AI Wave Survival. This mod is meant to allow for survival on any map, but is highly customizable, and works with any AI. (The included AI, "AI_WaveSurvival", is a dumb AI, builds nothing, and is meant to be used as a place marker for spawn points, but any AI can be used it its place.)
You can set the mod to spawn in defenses at the AI's spawn. There are different tiers of defenses, but that would certainly increase the challenge of attacking the AI's main base.
If you want an AI Game Style, instead of Waves of Units, you can:
-Disable all waves or set to small amounts.
-Set the Wave Style to "AI/Human Controlled." This disables the mods attack scripts. Otherwise the attack scripts force any spawned/built units to attack players. (There is another option, "Human with AI Assist", which can also be used with an AI Player. Only gives spawned units initial attack orders, but doesn't affect any built units. It will force a more aggressive playstyle from different AI's, if used with waves enabled.)
-Disable any of the Retaliation scripts, which trigger powerful responses to artillery and endgame units.
Or use the AI_WaveSurvival AI for waves, and give it AI Allies, which will do their own thing.
Since the mod has a LOT of options, here is a guide to help new players configure. Default settings have Navy waves disabled and are around an 800 rating level in challenge.
https://forum.faforever.com/topic/5563/ai-wave-survival-mod-information