Are you SURE you want nesting software or just a good CAM software? I'm not sure how slowing the feedrate on corners would do anything but make the kerf wider (??) maybe I'm too stuck in plasma technology but slowing it down increases the kerf.
It's financially dangerous to buy equipment and/or software of any dollar amounts over what you can comfortably write a check for BEFORE you can even project what kind of business you will have, what the potential market is (no, REALLY what people are will to write a check for) or if there is a demand big enough to support the overhead (and hopefully pay you too.
I think you will find that 90% of the cost of the water jet is in the pump, head, and recycling equipment. couple that with the fact you will need a commercial location with 3phase power (you can do plasma in your garage) and it should push you to research the technologies intensely. Your plan to put a waterjet on a plasma (and lose the plasma capability) may need deeper thought as well. I talk to guys every week that are building plasma tables to avoid having to pay a company to do waterjet cutting on metal. The amount you have to charge puts you out of the range of a lot of customers.
Just the operational cost of WJ or Laser makes them not price competitive with plasma or conventional routing for anything but the most demanding jobs.
Back to nesting. If you don't know exactly WHY you need nesting software and WHAT it does you will either: End up with junk that does not work, OR spend a lot of money for a tool that you will seldom use.
Just my personal observations.