We have dozens of projects in Jira and are creating more over time. We would prefer a project key length greater than 10 characters because we will shortly run into uniqueness problems with how we like to name and key our projects.

A length of 16 would serve us much better - 10 is too restrictive in our view.

The convention we use for project keys is:
[product abbreviation]_[release]

Examples:
PROD1_1311
PROD1_1312
PROD2_1401
PROD2_1405

Concerns we have are the following:
a) we have many product lines and we prefer the Jira project key be descriptive and recognizable
b) we sometimes have long release labels
c) we would prefer that dots(.) be allowed to better match our releases
d) we currently use [A-Za-z0-9_\.]+ for our custom project key pattern (regex)
e) we like to keep current with Jira, but moving from 5.x to 6.x is currently a concern because of Project Keys.