Good idea, and I also explored this idea and a year ago and also started building one, recognising a gap in the market for a solution that supports multiple LLMs, but also provides small businesses with a centralised managed AI client - billing, monitoring, logging, company prompts, etc.

Ultimately, I discovered https://www.typingmind.com, which offers all of these features. I am sure there are others - I was amazed that not more of these came out. Might be worth to see what they have built. The more of these that come out the better - its a whole new market.