method to keep private key in the open? say I have this private key: 5HpHagT65TZzG1PH3CSu63k8DbpvD8s5ip4nEB3kEsreAnchuDf

Now let's say I take the 5 out then take any location of this string and flip it:
bpvD8s5ip4nEB3kEsreAnchuDf HpHagT65TZzG1PH3CSu63k8D

(I kept the space to make it easier to see. merged would look like this: bpvD8s5ip4nEB3kEsreAnchuDfHpHagT65TZzG1PH3CSu63k8D)

Now I send this to myself on an e-mail. 

How easy would it be to reverse this string to the original privkey if you knew my recipe? (1. remove first char, 2. split key anywhere and flip)
How easy would it be to reverse this string to the original privkey if you knew my recipe? (1. remove first char, 2. split key anywhere and flip)


Absolutely trivial. An attacker only needs to try a few dozen combinations.

You should assume an attacker can try billions of combinations per second, at least.