DV the journey of 1000miles, starts with the first step. Here's an approach to consider.
1. What's the best upgrade chance? Either 7DII, 50D, or 5DII.
2. Get pics and measurements for all the three boards. This is research by asking tech supports who sell the parts, for info. before you purchase.
3. Ask a tech support for their opinion? They probably have thought about this already, and may be able to point out any obvious pitfall.
4. Now if all is good, buy the one that fits into your 700D (for instance), the PCBs I found were not that expensive. You may even want the tech support guy to do the install or write out the steps he would follow???
This is to minimize the risk, if you like H/w exploration you will eventually have to crack open a camera.
5. As for programming, that is probably not needed and if so that's what the ML team can handle.
Sorry Im too busy and have a shooting schedule for next few months.
Besides I would want to upgrade a 600D, as that would be pure hacker glory to have it shoot FHD raw. JM2C.
I think the time to explore the dual write s/w upgrade is after ML works reliably on the 70D. Which I hope nightly drops soon occupy me.