Yes the right person should be able to handle any or all of it.

If you don't do it right it won't necessarily be more suitable than it already is, and when that's the stakes there's got to be a responsible individual who can put in full-time effort however much it takes, with the resources appropriately allocated to back it up. The same CTO needs to be capable of single-handedly being the only "tech" employee, served by their own carefully orchestrated select contractors, or at the other extreme capable of building an in-house team to make things better from the ground up if more beneficial.

One person will have to make sure it comes out better than it is no matter what, or it's less likely to come true.

Regardless, it can be like servicing airplane engines in flight, so that's another outstanding skill to keep an eye out for.

Your and Fuzzfactor’s points are very well noted. To do this well we’d need someone who understands the domain/industry/business and who is able to set a coherent strategy. The rest follows from there.

Hi, are you looking for support to build a team out? Thank you.

there's another option: buy the vendor. in the absence of details, it's unclear if this is even feasible, but the vendor already has the software they need, it just needs additional work done on it. so instead of reinventing the wheel, buying the vendor allows you to fix the existing one.

I was wondering if a starting a new company was a better way.

It has one customer (initially).

If it doesn’t pan out you can drop that shitty vendor.

Or just the principal person behind the product. Careful approach and they may jump ship.