I'm perfectly optimistic for your project, just not so optimistic about my advice giving.
Roger on the WEST, in fact if you can get WEST cheap you are officially my best friend!! WEST Tech support is top notch. If you want to find out how best to bond to metal just call them if you have free long distance or try an email. G-Flex sounds like a bad bet to me. It is flexible, but is that what we are after here? (though I should point out the absolutely massive bonding area available over BBS and HTs probably means most things will work). To bond to aluminum in situations where the aluminum is enveloped, I just coat with resin, then sand the resin and the metal and just go ahead. That would certainly work, but there may be better methods. WEST as you know is a big exponent of hardware bonding, and the prep there is pretty minimal. Etching sounds like a good idea I kinda figured sanding in WEST was not going to let oxide come back at all. While no mater how you clean aluminum the oxide is back pretty much instantly which is the why behind AC welding and flux welding Al. If etching gets you there that would be good too.
Tubes are an incredibly weight efficient way of building a rod, but what the bike wants to locate in space is too complex for that model. The diamond frame is completely awesome for what it is, but there is also a degree to which it is like a skin kayak compared to a fully molded one. Anyway, I don't mean in the least to disuade you from building with tubes, just saying you have to deal with all the issues differently if you are going that route. If your frame is tubular rather than like a jelly bean etc... it will need different approach which will ultimately have some effect on your cloth selection.
By the way, check out bamboo making threads, blogs those often involve joining bamboo tubes with epoxy and carbon. And:
http://www.calfeedesign.com/
There are a lot of cheap carbon tube makers out there so it might make sense to start with that. For that mater WEST did an article on tube making recently, though I seem to recall they were mostly braided. Check out their Epoxyworks. There are some interesting tube videos on YT.
I don't find working with carbon all that different than working with glass. The stuff floats up a little, and it is opaque so you have to work carefully since you can see trapped air as easily, etc..., Carbon nudges people, at least in boat projects, to go all nutty high tech, so they start out building a ply dory and before you know it they are buying resin infusion planing software.
Structurally carbon is a big difference. It isn't forgiving. Very many carbon products have started out with models that broke, and that took a fair while to stabilize into something that was durable. I have seen the wars on fishing rods, arrows, now bike forks, etc... In the end these products often end up being the most durable in their segment for a variety of technical and marketing reasons, or not. Carbon lures people into making very light structures or into creating unexpected stress risers. Be careful with sanding, or any uneven surfaces that cause spikes in localized structural features. When making composites always remember what will stretch more than what, when you can share loads and when you can't. So imagine you have an elastic and you decide to strengthen it with a strong thread. The thread will not give so it will load first, and fail, then it is all up to the elastic. That is how carbon often behaves when bonded to something else. People figure they will share loads but the fail in sequence. Makes it sound complex, but there are a lot of people doing home projects with the stuff. I'm just rattling off the various things that have led to parts that went "bang" for me.
By the way. Ajax cleanser was apparently originally designed to clean aluminum surfaces for bonding aircraft parts. It does a good job cleaning.