I don't think that there is anything special about ATP and the time considerations...If you go to an FBO where you can fly 10 hours a week, or more, you'll get through in no time. Think about this:
Private:Instrument:Commercial:Multi engine land - commercial add-on with InstrumentCFI:CFII:MEI:
That's really not that bad, and I'd be afraid of flying more simply because
I feel it'd really start to interfere with you retaining what you learned.
All that said, you'll also save about $20,000 by going to an FBO rather than ATP, which is always good!