Transcontinental gearing

Hi. I’m hoping to be accepted into TCR#5 next year and have been thinking a lot about gearing options. But I don’t know much about bike mechanics, options, compatibility, etc., so I thought I’d ask for advice here.

I’d like Di2, based on the many reports of hand pain problems. I’d also like to have very low gearing options, because I’ll be dragging perhaps 10kg of extra weight (including food & water) up long climbs, and I’d like to main a relatively high cadence (e.g., not below 70, preferably 80). I don’t want to underestimate the need for low gearing. Doing 250+km/day for 2 weeks straight, in mountains, with bags, is probably going to result in extreme fatigue.

I’d also like whatever gear I buy to be as useful as possible in the future.

My current thinking is to buy a bike (let’s assume I get a new bike, for simplicity) with Ultegra Di2, compact (50-34) or sub-compact (52-36) chainrings, and an 11-32 cassette. Then, swap out the crankset for a 46-30 to use in the TCR. I guess I’d need a chain spotter for the FD, perhaps like this. Once the TCR is done, I can put the compact back on and live happily ever after with Di2 and regular road bike gearing.

Based on reading and some calculations, I’m estimating (hoping!) the low 30×32 combination this setup would allow me to get up whatever I need to.

My main question is what 46-30 crankset would be compatible. E.g., this FSA option looks nice, but I don’t know enough about bottom bracket standards to know concretely what it would work with. I can see other options on the web, but I feel quite in the dark as to what will work.

Questions…. Does this sound like a good approach? Will it work? What other gearing options might be worth considering? I’ve also read that Di2 can be made to work with an 11-40 cassette via the use of a derailleur hanger like this, so that might be an option (with a compact up front).

I’ve kept the questions above focused just on gearing, but I’d also be very happy to hear opinions about bike options too. I’ve looked at a bunch, of course. But maybe that should be a topic for another posting.

Thanks for any help / thoughts. It might sound from the above like I know what I’m talking about, but I really don’t. So I could easily be overlooking very basic & obvious things. I’m very much a novice on bike componentry.

Terry