A/B testing of posts with unique URLs for each variant AND editing in custom fields

I’m wondering if anyone could offer advice on how to think about creating an A/B testing plugin for posts that:

A) lets me assign unique URLs for each variant post^**1) and**

B) is customizable on the frontend (i.e. new-post.php).

There seems to be two ways I could go about doing this:

1. The first way: Create three separate posts, use the Shrimptest plugin to test, and exclude two of the posts from single.php (This was basically the answer that Otto gave when I asked about it on Stackexchange. The problem with this solution, though, is that I would have to go into the files to edit the code every time I want to test a different batch of posts. And I can’t figure out a way for it to meet requirement B.)

2. The alternate way: Create custom fields in new-post.php that would give an editor the option to write in alternate headlines and upload different Facebook images and FB text. This is my preferred option right now since everything would be customizable from new-post.php. The problem is that I’m not sure how to meet requirement A (a unique URL for each variant I test). Is it even possible to create a custom field in new-post.php that assigns sub-URLs on top of the default URL?

Any tips or suggestions on any part of the problems I described would be great! Thanks in advance!

Note:
¹⁾ The reason I need requirement A (unique URLs for each variant) is because I ultimately want to measure shareability of my posts on social networks.

For example: If I launch a post with Headline A, FB picture B upon sharing, and FB text B upon sharing, I want the number of clicks on that A/B/B variation to be tracked. Thus I need to assign a unique URL to that variation.