The mystic cannot model and simulate his or her apperceptions* during mystical union because in that state there is a cessation of change in the perceptual field. Therefore, as Kant stated, inner time, the very essence of this kind of simulation, does not exist after that cessation. However, the mystic can model and simulate the apperceptions before the cessation.
The period before the cessation is known in mystical literature in the West as the refiner's fire, the dark night of the soul, or purgation. In Zen it is called overcoming samsara. During that period, which in my case was 10 or 11 hours, the mystic's heart opens and is purified and his mind becomes one-pointed. This period prepares him for mystical union. Important teachings of religions throughout the world are based on insights mystics have brought back from their experiences of the dark night of the soul and mystical union. If there existed an accurate model and simulation of an experience of the dark night, deep insights could be available to peoples of all religions and to students of philosophy, as well as to cognitive scientists, neuroscientists, and others in various scientific fields. Such a model could also give insights about mystical union, because it could tell us about the mystic's state at the moment just before the cessation when he passes into union.
2) Please also see item 13 of the 'Tentative Conclusions' page for further insights on timelessness.
* apperception: later recall of the continually changing horizon of the perceptual field during an experience.