i would suggest he will determine how his travel has changed from a business traveller to a student one. Ultimately his question suggests he is evaluating either a backpack as you suggest or a travel pack that I have suggested.
While this is not the lightest bag, its utility is exceptional. Its 60L when combined together only: the main bag is 40L and the rest is in the detachable (20L) daypack.
http://www.ospreypacks.com/en/produc...ab=description
I have carried it on Air Canada as well as LH,LX, MS, TK and will be doing the same on BR, SQ and UA in a few months.
IMO, It allows the most flexible travel, but if his intent is purpose backpacking then your examples are more appropriate.
However, if its a mix of trains, planes and automobiles, with airports, hotels and other venues, this is worthy of consideration. Really depends where and how he is travelling.
I have used it extensively and the extra weight isnt noticeable and is offset by utility.
It was awesome for travels through Africa last year, this past summer in southern Italy, Croatia and Czech Republic and will be taking it to Bali and Australia this year.
There is also a review here from others that used it for an 8 month trip:
http://artydubs.com/2013/08/27/ospre...-and-counting/
Ultimately, the OP will decide whats the most important to meet his travel plans, and am merely providing suggestions supported by experience if his priorities align with mine.