This is where some up front validation is handy. You have an assumption that slack is what everyone would want, but do you have any data on this?
Would other integrations be beneficial?
What's the feedback you're getting when speaking to companies about this?
Is this a problem that people are trying to solve?
It looks like it could be useful in your future plans, but really honing your value proposition as to what problem you're solving for the startups would help on your marketing I think.