There’s a lot of advice here regarding the dangers of your plan, and I’ll add a little of my own, but I’d like to offer one note regarding why you are correct f

There’s a lot of advice here regarding the dangers of your plan, and I’ll add a little of my own, but I’d like to offer one note regarding why you are correct for considering this. What exactly is the nature of this software you’re running on? Is it an aged or decaying platform? Worst case, is this a PHP thing that has to have updates carefully monitored in the event of eventual security breaches and hacks? And what exactly is the health of the software provider? If they can’t be bothered to respond to you and the sort of budget $300M/year can afford… I’d be sweating bullets for sure. You need to have a plan for them just disappearing one day. --- That said: I just committed the cardinal sin of helping to buy a company that had a decaying software stack, thinking that we could just straight up replace the whole software stack. Gave ourselves a big fat year of development and a big, experienced team, and still couldn’t pull it off in time. Harrowing experience. Someone else here suggested getting a small freelance team and "letting them go nuts." I think an approach where a small team was building new, independent microservices that supplemented your main stack, and then gradually replaced features — until finally just a small core was left to be replaced with something modern — would be a feasible approach. This would need to be a very long-term plan with a lot of commitment.