Upper management need to understand the problem and the options and need to buy-in on whatever you want to do. Practically: cut the bleeding, get the current t

Upper management need to understand the problem and the options and need to buy-in on whatever you want to do. Practically: cut the bleeding, get the current team at least using version control and working with a CI environment. That will be a lot of effort (been there before with a similar .Net product but much better team). Then you're going to need significant resources to re-build on a modern architecture. I would simply go with releasing another product if that's at all possible. You clearly have some market and channel to sell into. Just beware: this sounds like a problem which will take 3-5 years to solve and whose chance of success is dependant on organisational buy-in. So you need to ask yourself if you're willing to commit to that. If not, quit early.