What should a coach consider when constructing a personalized training plan?

I'm a software developer and as a pet project I've started working on a 'personalized triathlon training plan generator'.

A few of the input parameters that should go into creating a good training plan are obvious (race distance, time available), but what else should be considered?

Some that I've considered:

* Race distance
* Start and end date of the plan
* Total volume level
* Available time (per individual weekday)
* Discipline priority (ie, I need to focus on my swimming)
* Current level of fitness (how quick can the intensity/volume build-up be?)

Thankful for all input (pun unfortunately intended)