[O] Is it possible to implement a TARGET date in addition to SCHEDULED and DEADLINE?

[M]

I wonder how difficult it would be to add a 3rd "TARGET" date to
headings/tasks, which is treated similar to Deadline and Scheduled dates
(can be used in agenda, can be easily set and modified, ...) :

example:

* TODO [#A] My org-mode task
TARGET: <2015-04-01 Mi> SCHEDULED: <2015-03-30 Mo>

Background:

I often use "artificial deadlines" to specify that a certain task shall be
done until tomorrow (or another date).
And this date is neither the starting date nor is it a real deadline.

Up to now I'm using the DEADLINE date for this purpose, but I don't like
that solution, as it is confusing for me to know which deadlines are real
"hard" deadlines (e.g. I have to send in my tax declaration until a certain
date and not one day later) and those artificial ones, which  not carved in
stone. 

So is there an easy way (I don't know, how modular org-mode is set up) to
add this 3rd TARGET date to org-mode?

Martin