Take a close look at Bench Accounting (bench.co), particularly its features page (https://bench.co/features/) which should give you an idea if it is a fit. It is a combination of the bookkeeping technology along with actual bookkeepers so it is a technology-enabled service (end-to-end) but does not offer tax accounting or more complex outsourced CFO functions. Might be a good fit for you (full disclosure, I'm the CFO at Bench). Hope that helps!

My suggestion would be to connect (face to face if possible, Skype otherwise) with a couple from each category of users quickly (and multiple genres if that is an important category for differentiation) and then look to work towards the MVP,before getting more feedback (and ideally sales). Important to get that some of your initial consults are with users/customers outside of your network to ensure there isn't some kind of friendly bias.

You may want to consider showcasing the more narrow, focused application which will be (ideally) your more capital-efficient beachhead that proves the product and market fit. Meanwhile, I would present a few select slides or datapoints from the original presentation as something that showcases the broader opportunity which can be pursued at a later milestone or development stage.