If you want to go to Hollowtech II and outboard bearings, Phil Wood make a pressed in outboard bearing set up for Kleins.

Phil Wood & Co.

Phil Wood also sells Klein compatible spindles in a variety of lengths and both ISO and JIS tapers. (Even Ti spindles.) There is nothing wrong with a quality square taper crank.

this looks like a great solution, but it appears as if they are sold out. I'm going to check and see if Hope makes a press fit in the same size.