as for the exchanges.. pretty much all the coins will be on all the exchanges
You are making contradictory statements (as always)
It is no use supporting the coin which doesn't get traded (read listed) at major exchanges (and Coinbase is nowhere near being one). If we compare the impact of exchanges versus merchants on Bitcoin price, the latter will suck heavily as you yourself say ("pretty much all the coins will be on all the exchanges"). It should be obvious that most of Bitcoin value comes via exchanges, so Coinbase, Bitpay (or any other payment processor, for that matter) with their shopping cart API's will be utterly irrelevant if exchanges refuse to support a certain coin
im not being contradictory at all, i just see things layers/dimensions deeper than most
Your layers (dimensions) are mutually exclusive
You basically talk about Bitcoin value which stems from its transactional utility (i.e. from Bitcoin use as a means of payment) in your convoluted way but you still ignore the fact that this utility is minuscule at best (or just outright ridiculous). Most of Bitcoin value comes out of sheer speculation, and that's where its utility exactly equals its nominal price (remember, "buy low sell high"). As you can easily guess, exchanges are the place where this speculative utility is born, just like the transactional utility is brought about by merchants accepting Bitcoin as a means of payment for their goods. The lesson to take home is that the impact of exchanges is devastatingly overwhelming that of merchants and which can be safely discarded for most intents and purposes