When I think of business cryptocurrency financial stuff, I also think of those things. Employees need to be paid, and they might want their paycheck in crypto or in fiat, or a combination of the two. Vendors that need to be paid will usually just want fiat, either through some kind of fiat electronic transfer, or a "bill pay" check that's printed and mailed.
The problem is that payroll is HARD. That's why banks, who handle business accounts, don't do payroll and it usually falls onto specialist companies. Given the "global" nature of cryptocurrency, many of your customers will likely have employees spread across the world, which also adds payroll complications when it comes to withholding, legality of cryptocurrencies, etc.
You might want to just partner with a payroll company otherwise you'll find that most of development (business, software, and legal) will end up being sucked into that blackhole side of the business that doesn't even have a high margin.
Paying vendors? That's relatively simple in comparison. That's why most banks DO provide bill-pay and transfer services.
What I suggest for your "secret sauce" is being very internal bureaucracy friendly and give out employee corporate debit cards freely.
Build your system so when a business signs up, they can make accounts for all their employees and managers and set up authorization workflows. If Bob in accounting wants to buy a new chair, he should be able to submit the request for the funds. If it meets various criteria (ex: less than $500, only needs manager approval and not department head approval) and gets approved, then your system makes the cost of the chair (plus some buffer) available on Bob's wallet which has a linked Multis debit card.
If the business only provides debit cards to managers and up, then it would make the funds available to the managers crypto wallet (and associated Multis debit card) so they can purchase Bob's chair.
Lastly, if you put in place this support of business organization structure, use the same structure for the multisignature systems. One of the signatures could be Bob's manager, or maybe it would require the manager and the department head, etc... But not Bob and his wife, who happens to be a manager in an entirely different department at the business.
I've done crypto work before, and also have recently build a "corporate bureaucracy friendly" authorization system for a SaaS I'm working on so putting those two experiences together seemed natural :-)