I think the assertion that this would save the average club racer money is spurious.
If one were to follow this trend to its ultimate conclusion what would actually happen is that racers will own/use a different car for every track/surface they race on.
(Some lucky Tamiya drivers already take along and choose from two 4wd and two 2wd cars per meeting and how many Kyosho runners do we know that always bring along a DB1 and an RB6?
)
This is great for those that can afford it but will make it impossible for those on a budget to compete on a level playing field, thus prompting a return to the elitism mentioned earlier in the thread (re. brushed equipment).
Moreover the purchase price of a dual purpose model will, inevitably, be higher than a dedicated (simpler) 2wd car thus serving further to deter possible newcomers with a limited budget, that can't be good can it?
That said fair play to those who have found a 'loophole' in the current rules that enables them to improve their performance, I wish I could find a way to improve mine!