You'll get so much more power down in a 350bhp mk5 compared to a 350bhp mk4. The chassis and suspension on the mk5 are a complete redesign. Much better.
That said, anything north of 350 bhp & lb/ft will still be getting close to the mk5's comfort zone if it's not driven gingerly at certain points. There's plenty you can do to get around that in terms of upgrades though. LSD, sticky tires, coilovers, bushes, mounts etc. Also you might be able to get it mapped to limit torque in the first two gears.
Personally I'd go stage 2+ on the standard k04 - so around 350bhp. See how you find the power delivery. Then do some serious thinking about those chassis mods. Get the car to a point where it copes as well as it can in terms of traction with the standard turbo. Then if you want more power you'll be ready. Might need a couple of extra mods for the hybrid, like a TTRS low pressure pump, and obviously another map, but you'll be pretty much good to go.
I wouldn't be tempted to stick the hybrid straight on until you'd nailed the handling/grip side of things.
