I am considering building a startup that provides a user with twitter profile score i.e. how good is someone twitter profile before someone follow them. I have basic consideration about what factors to involve, like:
The first thing I would consider is how is the service you are offering going to be any better than the available options:
The question is how're you going to monetize this? I've often thought of creating something similar for free, which gives users a badge they can put on their website or blog, and that they can tweet about. The aim would be to promote a paid Twitter SaaS I run. For this, I would copy existing metrics, but make the graphics super-sparkly. So, in my mind, this would be part of a bigger marketing plan.
I think you should start by thinking about the bigger picture: what can you promote by creating this tool. After that you can decide whether you need super-clever metrics, or can get by with standard ones.