DA15 + DA18-135 is agreat combo! the F70-200 will only add the 135-200 range which is not taht much... If you want extra reach you should consider your F100-300 but I donīt know about its IQ. The Takumar 200mm is slow so I donīt see any advantage over the zooms...
I would take:
DA15+DA18135 for trekking
F28+F50/1.7 (vs 2.8 macro: faster to autofocus - biggest aperture) for creative / indoor fotography
From what I have read, the DA18-135 is also excelent arround 24mm@f5.6/f8.
Honestly, I think the DA18-135 will stay on your camera most of the time. The size of the DA15 makes it great to carry in a lowepro lens case (
Amazon.com: Lowepro Lens Case 8 x 6 cm -Black: Electronics) for the moments you need wide while trekking (you will trek a lot...)
finally, get a CPL for the 18-135, you wonīt regret it. (also, a 49mm one for the F lenses if you can afford it or a stepdown ring..) (
Amazon.com: Marumi DHG Super Circular Polarizer CPL PL.D 77 77mm Filter Japan: Electronics)
when out at night (taking a nap is the law becouse of the heat so night life is really good) you will want the IQ of the F28 wide open and the F50/1.7 for low light speed and a bit more reach.
Have a nice trip and please show us some pictures when you get back!