BB/PF has the advantage that it can use every crankset available, just get an adapter. 24mm frames can only use 24mm cranksets.

What do you mean by "24mm frame" ? Any frame can fit basically any crank based on 2 prerequisites: (a) you have a proper BB insert (b) crank spindle is long enough . If these two are fulfilled, then even a frame typically specified for 24mm cranks (bsa,bb92 etc) can accept a 30 mm crank. That is basically what I outlined in my opening post. Of course issues with chainline and QF remain, but it's a separate problem.

With an adapter of course http://wheelsmfg.com/bb-30-shims-shimano.html

It depends on the group you are using, if you go with SLX mentioned above, BB should be included with the crankset.

Yeah, reliability and ease of maintenance together with universality makes BSA a very solid choice. Still, if I could get benefits of both systems, why not to try Not to mention that SRAM GXP BBs do not have the best opinion in the world, so I'd like to avoid them if possible (yes, there are counterparts from Aerozine etc. if needed).

I wanted to share some thoughts on the thing I've been long thinking about, something which would help me when I finally get to build my own chiner.

One can argue about superiority of one standard or another, the way I see it:

BB30/PF30

+ lower Q-factor available (no BB housing, shorter spindle)
+ often a tad lighter
+ 30 mm spindle stiffer

- creaks in the BB are very hard to get rid off, can't replace the BB housing itself (BB30)
- pressed connection less reliable in general threaded

BSA

+ threaded BB - more reliable and easily replacable
+ larger spacing between bearings - stiffer system

- only 24 mm spindle in most systems
- usually a bit heavier

I began wondering if there is a possibility of merging these two systems to have stiff and light crank with 30mm spindle and the replaceable and easy to maintain threaded BB.

It seems that some big players had the same idea recently:

Rotor
Race face

Unfortunately, these parts are priced pretty steep and I dwelled upon the idea of developing a more affordable alternative for 1x10/11 systems.

As far as I know SRAM BB30 cranks come in 2 spindle lengths:


One  can see that 6.5 mm difference in spindle length corresponds to 6.3mm difference in spacer width, so far so good.
For both BSA and BB30 (MTB) the BB shell width is 73mm. Substracting it together with the spacer width from the indicated length leaves about 13mm for DS arm installation (it could be less, that's why the 6mm wide counter ring is for).

I considered the case, let's take the long spindle version of the crank, get rid of the spacer and get rid of the counter ring. You get 101.5(spindle)+6(counter)-73(bb shell)-13(DS arm)= 21.5 mm of free space (or more if DS arm doesn't need full 13mm). Seems enough to fit the BSA30 bracket there (10.75 mm for each housing, bearings themselves are 7mm each).

In fact a guy on MTBR performed such conversion with the shorter spindle XX1 crank and narrower (old) 68mm shell:
MTBR
I asked him for clarification and he is convinced that idea above should work for a standard frame and longer spindle as well.

Two issues possible issues can occur, however both can be countered IMO:

- there is some space left and without counter ring there is sideways play in the crank (I think it can be corrected with (wave) washers, as it shouldn't be more than 2-3 mm)
- chainline could broken (this one is more complex, however from the DS point of view the ~10mm bb housing now acts as a spacer. That's less than 1mm difference compared to the spacer used in the shorter spindle. Therefore, any spiderless NW ring or spider for more 2x/3x setups designed to work with short spindle should work here as well)


That's it. Unfortunately it's just theory crafting on my part as at the moment I have no means of testing such setup. Perspective of using even BB30 x9/X0 with NW chainring on BSA frame is very tempting though.

Any input/thoughts appreciated. Of course if anybody here has a friendly LBS who would like to put this theory to the test, I'd be great.
 

I agree with heart rate, 220-age is the crudest approximation. Still, for the bike fitting part it's very good.

Was also considering Venture SL 650b, there is a guy on lightbike.it forum who seems to be happy with it. There have been a lot of people with 29er alternative (Gaea), very happy with it. So I believe that while FS frames from them are problematic, hardtails should work quite well.