I just rang Qantas to ask the specific question. I was told that I could "put at risk" my return journey. Why? Because once I was flagged as a "no show" on the Lon>Paris leg it is possible they would cancel my return flight.
When I asked if I could avoid that by simply phoning Qantas and confirming my return leg, the answer was - well - somewhat evasive. He simply said I shouldn't "risk" it.
Is anyone aware of actual instances where this has happened or is Qantas just trying to "pull my chain" [as the Americans would say]?
The practice you describe is called "throw away ticketing", i.e. purchase a ticket but only fly part of the trip, throwing away the remaining sectors by basically no-showing.
They won't tell you the specific consequences and it is likely those phone agents don't know. Either that or (and this is a genuine reason - "rock and a hard place" dilemma) they are not in a position to tell you that you can't do it, because no one can stop you from doing it, and they cannot tell you what will happen to you, because any number of things could happen to you - including nothing. For the agent to tell you the consequences and nothing happens, or the wrong thing happens, would later be construed as a lie. Even if they said, "<such and such> may happen to you," if nothing happens or something not covered within the <such and such> happens, again you will think it's a lie. So the easiest way out is to say not much except "don't do it".
The anecdotal evidence around suggests that some people will not be caught in throw away ticketing practices. This seems especially true if you have no further travel on the same ticket. On the other hand, airlines that catch passengers practising throw away ticketing may do any number of things, from cancelling other tickets, forcing payment of fare difference or blacklisting. Now some of these may be legally contestable (especially in the EU, where consumer groups have been forcing airlines to become a lot clearer on throw away ticketing, i.e. if it is against the rules then make it so
and comply with EU consumer laws), however at best remember that you will need to be ready to defend yourself (even if you are a shoo-in to win a case, it still requires considerable groundwork).
Even if you do it and legally exonerate your actions, the airline can still blacklist you (which you may not mind at all, mind you).
Basically you can avoid all of these headaches by not doing it.
I must stress that I only did some limited searching and uncovering a few anecdotes. Do not take any of the above as binding or legal advice. I will stress again - if you choose to do throw away ticketing,
you may not get caught at all. If you do get caught,
I do not know what may happen to you - it may include nothing and it
may (not will) include blacklisting.
Am I better off just paying the fee over the phone and getting a Qantas agent to lock me into one?
Depends on how important the tickets are to you. If you really, really want them, and you can't find them, then definitely it is worth it. Considering how difficult it is to get seats on the route you chose and perhaps at the time you selected, you may never be able to find seats on that unless you take this offer.
I think it's not bad Qantas found something for you. Sometimes they will simply confirm that you found nothing (and their "screen will tell them the same"), and you're simply out of luck. Here you're being given an option, albeit a more expensive one (i.e. paying the assistance fees). You should weigh up whether the extra costs in assistance fees (points or cash) will be better than simply paying the airfares outright in cash.
As my first venture into actually using FF points, I have to say there seems an element of smoke and mirrors about the "real" benefits.
QFF are quite sparing with awards as it would seem, although again I emphasise that you have picked a popular route and period of travel.
Also, for those who are of higher status, it generally gets easier to find and book award seats. This is intended to allow more loyal QFF members to access seats which may otherwise be snapped up faster by lower status members who may simply accumulate masses of points (e.g. through extensive credit card spend).
Try another period of the year or another sector - you should find that you can book awards at those times. They don't match what or when you want, though, simply because of the demand in the dates and destinations that you want to book (both for cash tickets and award tickets - and if you can get people buying cash tickets without trying, then why would you open up too many award tickets?)