Performance of Virtual Machines on MacBook Pro with and without discrete graphics
I run three ubuntu VM, light garage band or Logic Pro and Safari, FaceTime and Apple productivity apps on the 2015 MacBook - base model, base storage, base RAM.

You'll have significant CPU hogs choosing Chrome over Safari (in general), Skype over iMessage and Office over Apple's Apps. 

Whatever Mac you push with that workload will become thermally overloaded and throttle the CPU, and since you want the Mac to last for half a decade, you might as well get the best CPU, most RAM and go for the 15 inch model.

You could run all the apps on a lesser Mac, but if you don't care how hot it runs, get the most watts you can pump out and you'll have the best performance.

You want the 2.8 GHz CPU, so you get a better value with the dual GPU option since you get another 2 GB ov VRAM which will get used / free up some of the 16 GB main memory for other uses.

If you doubt the 2.8GHz Quad-core Intel Core i7, Turbo Boost up to 4.0GHz is enough, you should get a lesser portable and run your VM on a desktop even if said desktop is a Mac Mini.

You also might consider getting a MacBook / 13 inch and combining it with an iMac for the cost. Much better VM, but you don't carry it all with you. Remote access to a VM isn't any slower than running the VM locally - in fact, it's probably much faster with a desktop CPU instead of a mobile CPU where much more energy can be had, much more heat dissipated and more bang/$.

Good luck buying. It's an interesting CPU and RAM centric workload, so you have lots of good tradeoffs to make - every $ you upgrade will give you noticeable benefits, so it's really what your time is worth and how much sacrifice you'll endure to buy the top of the line or two Mac to run that workload.