Yes, if SIAF distributes half the TRW-shares (like they've promised) then half of the dividends would go to (current) SIAF-shareholders. How does this translate into noone wanting to own SIAF anymore? (although we do need some support for the PPS post ex date!)
SIAF can still give the dividends from it's retained 18.3% to it's shareholders (although it would be half of what it can without the stock dividend), but now SIAF also will have a non-deniable proven record of being extremely generous towards its shareholders... So when SIAF then states that it's preparing a stock-dividend of CA, then the market will KNOW that SIAF means it and respond way better than it has done so far.
Also, after the TRW-financing and/or CA-deal SIAF doesn't need that extra cash from the "lost" TRW-shares :-)
Not sure why you think it is a risk that TRW would not want a loan and/or ipo - why wouldn't the partners want the growth-story (which they have partially paid for already btw) and a decent P/E? Also, it will be difficult to trade TRW-shares before the listing - so SIAF should easily gather most of its current 36.6% voting power through the shareholder's of SIAF and hence not loose any real power if that risk was real.
Also I don't understand your speculations to why SIAF would want a higher valuation of TRW. It is obvious that there were some "power struggle" to how the ownership of TRW would end up, so why would SIAF try to boost the book value of TRW?