Part-time employment after getting the GC

[Mette]

I have a hypothetical question: what happens if after you get your GC the business situation of your employer changes and instead of firing you he just offers you to work part-time at the exact same position stating that as soon as the situation improves he'll have you back full-time? Will you be in any trouble in this case? People say you're OK if the employer fires you since you always had an intent to work for him permanently. But what about part-time? You're still with the same employer, you're still doing the same stuff waiting for the situation to improve.
And what happens if a person needs to switch to part-time due to medical or family reasons?

[Mette]

Anyone? Any ideas?

That's what I found on Attorney's Murphy site about Change in Salary (because basically that's the issue with part-time)

"The economy is not a constant. We have seen in the last two years that the salaries for many high tech positions have been reduced. The dramatic changes generally have been from the time of filing the labor certification until the adjudication of the I-485 application. If the applicant is past the 180-day threshold and has been informed that the employer will not pay the salary listed on the labor certification once the green card is approved, the applicant should consider notifying INS that AC21 portability provisions apply in his/her case."