I have posited a similar idea with some of the people I work with. The issue of having complex, multi-step tasks be completed successfully has already been solved. You don't heavily invest in having one single expert for your business to solve all your problems. You build a team. Multiple specialized experts working in unison to achieve a shared outcome. Some people work on the task simultaneously, others sequentially. All with a specific purpose associated with the goal.

These assets are horizontally and vertically scalable based off skills, quality, or performance required. An efficiently designed AI architecture I believe could do the same. Its not mixture-of-experts as you aren't necessarily asking each model simultaneously but designing and/or having the system intelligently decide when it has completed its task and where the output should travel next.

Think of a platform where you had 'visual design' models, 'coding' models, 'requirements' models, 'testing' models, all wired together. The coding models you incorporate are trained specifically for the languages you use, testing the same. All interchangeable / modularized as your business evolves.

You feed in your required outcome at the front of your 'team' and it funnels through each 'member' before being spit out the other end.

I have yet to see anyone openly discussing this architecture pattern so if anyone could point me in that direction I would thoroughly appreciate it.