Good idea but the problem is that VA made platinum too easy to get, have comped and matched so many members that I think the numbers even at a 'plat only fly ahead on all fares' might honestly be too much for them!
Also this decision was made in conjunction with them significantly downsizing their fleet and passing routes off to Tiger = less seats all up available to play with for this sort of benefit...
The benefit was always subject to availability of seats (and officially only seats in the same fare class) on the earlier flight, so I don't really see what you mean. It was always a self limiting benefit, which would have been difficult to exploit if either (a) most of VA's flights were fully sold and/or (b) too many people were entitled to Fly Ahead. However, IME Fly Ahead was available more often than not, which suggests that neither of those things happened. And that was when this benefit was available to both Platinums and Golds. As such, I see no reason why it could not have been limited to Platinums only if they wanted to limit it at all - despite it being easy to get Platinum, there are still clearly a lot more Golds than Platinums.
As for it being too easy to get Platinum - I think that is true, but the solution to that problem is not to strip away the benefits of Platinum. If that really is what VA were concerned about, then they should have focussed their efforts on increasing the hurdles to attain/retain status, or even introduced a new Platinum One or equivalent status level, with additional benefits. To provide context, over my three previous membership years, I earned over 5,500 Velocity SCs, averaging over 30 sectors per year on VA metal, in addition to a lot of OS travel with their partners. So I am sure you can understand why I'm not happy with my benefits being stripped away because of a perception that other people got Platinum status too easily.
The fact is, Velocity have removed almost any incentive for me to pursue Platinum status, so I'm no longer bothering. Half way through this membership year I have 560 SCs, but 520 of those came from one EY trip that I booked before the changes were announced. I have flown only 2 eligible sectors, and I have no forward bookings on VA or their partners. I might still end up retaining Platinum, but I'm not going to make any special effort to do so. So the losers here are VA, and the winners are QF. I got QF Gold very quickly through a status challenge, and I should get to Platinum by the middle of next year. I realise QF are not perfect either, but as things stand they are way higher in my estimation than VA, and that means VA will no longer get much of my business - unless their fares are significantly cheaper, but the fact is that they rarely are these days.