As others have mentioned, building custom homes is the last place I'd use AI.

But if you're considering a pivot, interior design would be a great direction!

Given the space and furniture I have or could buy, what are my alternatives for flow and light and usability? What if energy or allergens are an issue?

This could engage users and has natural add-on's for buying things that would help monetize with price discrimination. End-users could be happy to explore, but you might have more features for designers.

You could fine-tune based on all the home-decorating videos and materials, add MCP for physical models (layout/positioning, environment), and use video models for ingesting current and visualizing results.