4k Hardware Strategy

Looking for some general strategy advice as I upgrade my systems for editing underwater 4k footage (XAVC footage from a Sony Z-100).

I'm currently using a late 2012 13" rMBP w/ 2.9 Ghz i7 and 8gb of memory. I'm shooting and doing dailies in the field, which is a bit painful with my current machine, transferring everything to multiple 2tb USB3 drives (that are likely too slow for the work I'm doing).

I then tend to edit back in the office- it's nice to have the ability to edit from the field, but not a requirement.

So, I'm considering the following options:

1) Upgrade to a maxed out 15" rMBP and purchase dual 4k displays, allowing me to do dailies in the field and then edit and preview 4k footage.
2) Upgrade to a Mac Pro (specs?), with dual 4k displays, and keep the 13" for dailies/travel.
3) Upgrade to the new 5k iMac instead of the Mac Pro, and keep the 13" for dailies/travel.

I guess a last (maybe best) option would be to go with 2 or 3, but also upgrade to the 15" rMBP, though I like the size of the 13" for the amount of travel I do.

Lastly, any suggestions for storage/drives would be appreciated considering I'm working in the field and back in the office... often for up to a month at a time.

Thanks in advance for any input here.

Can you work with Proxies on that 13" Macbook Pro?

Yes, it's just a bit..challenging, but that's the route I'm taking. I just ordered the new 5k iMac, maxed out.

By the time 13" rMBP dies or becomes outdated, I'm sure there will be one that makes dailies/proxy a bit more efficient.

Also, I ordered a pegasus raid system for the iMac, but does anyone have recommendations on fast, high capacity drives for travel?

If you can take the iMac with you they have carrying cases for it.

I know a few people that take iMacs on the road.