Not that I am aware of.
In 3CX the templates are set for one account, one extension. The templates are positionally dependent. That is to say that using the one account, one extension philosphy, if you could provision using one extension first, the provisioning of the second extension would simply overwrite the first extension's attributes. They will both use the same template and write your varaibles into the same fields. The MAC address prevents this.
I am guessing here, but my thought is that given the broad array of phones available, there are simply too many variances as to the number of lines/accounts and features per make and model of phone to make use of the common interface as it is today. Further positioning the data on the phone itself makes it even more problematic.
To illustrate, I have a Cisco509G which can accommodate 12 lines. I use this phone as it allows me to set accounts up directly on my newer clients' systems so that I can monitor at a glance and they can reach me with one button. Now assume for the moment that I want to have two buttons associated to the same account, but with two different extensions (same as you), but I want the button on the upper right and upper left to be the ones lit. This would positionally represent locations 1 & 5. 3CX would need to abandon their "one size fits all" screen interface and develop one specifically for the 509G so that I could accomplish my desire. Additionally, there would need to be programming logic that preserves or warns of existing variables should more extensions come into play at a later date for the same MAC.
You could alter the template, but no matter, it is a manual process. I would likely stay mdoifying the phone and then upload the configuration fot safety sakes.