Hey David, not trying to sell, but for some context - I am part of a revenue agency and part of our offering is SDR (global one, working with enterprise and scaleups mostly). We are experimenting with automations and different sets of integrated tools to fully automate outreach and nothing is yet good enough.
If you have a wide market, you can try Clay, Apollo, Expandio and a few others to create a workflow that will scale the outreach to tens of thousands per month, but will again need at least 1 or 2 people to set up, fine tune and generally improve the whole workflow. I don't recommend this as I see it to be a race towards the bottom, but may give some good results for a period of time (and obviously I am a quite biased).