I'm leading an in-house team that's developing a custom software for a niche financial institution. The original product was outsourced to a software factory, forward 2 years and they decided this project wasn't worth their time and left. I took the responsibility of moving the project forward, then with only another dev.

What worked great to me as dev?

. the direct connection with the CEO as he became a high level PO. With this arrange we were always sure that our work was giving value to the business.

. I learned a LOT about the business and loved it

. I was in charge of growing the team when the amount of work justified it. I got several wonderful devs onboard.

What worked great for the business?

. they decided and prioritized the direction of the (customized) product.

. they understood the strategic constraints and possibilities of their software

what was tough for all?

. at least the first full year, was spent killing bugs and making the project work properly. Operations needed too much support in that initial period. Stressfull times.

Starting with a pair of Senior Devs is a good choice IMHO. If you trust them, even better.

Those points I mention above that I found great, are your selling points to hire some good Developers.