Your questions appear to revolve around the aircraft type used by the team, but it most respects, as far as the RAAF is concerned, the aircraft type is a secondary consideration. It is driven by the unit that provides the team. Since the 1960's, the unit that has provided the official display team has been the Central Flying School. This is probably a good choice as the unit is the RAAF instructional standardisation unit, and does not have an "operational" ie front line focus (as opposed to, say, 76SQN/2OCU etc). This means the job of balancing competing priorities is less difficult.
So, whatever aircraft CFS operates will be the type the official team gets. From 1970ish to 1989ish, CFS operated the Macchi (
), so that's what the team got. After that, the unit reequipped with the PC-9, so that's what the team got.
A question that is often put to the team is, "why don't you guys fly the Hawk?".....see above. Another reason is - be careful what you wish for. Relatively speaking, the PC-9 is an aircraft with a low landing speed, short runway capability, low ACN (a number that determines whether the runway and tarmac of a particular airport can handle the aircraft "footprint"). It can, and does, operate from grass fields. So, the Roulettes are able to range far and wide to present the show and represent the RAAF in many places they could not operate into if they were flying the Hawk.
In these times of increasing scrutiny over every defence dollar spent, the fact the Roulettes are (a) a part time team, (be) operate an inexpensive platform and (c) can deliver the show to the majority of locations in the country should deflect most criticism about having such a team. This is certainly a position that many full time jet teams overseas do not enjoy.
So, to answer your specific question: yes, the Roulettes could certainly put on a more exciting show flying jets (Hawks/Hornets). But could we afford it? Could we justify such an expense? What would the opportunity cost be? Who would get to see it? How often and where could they fly?
I put it to you the RAAF has stuck with the arrangements it has for the last 40 years because they appreciate that for an airforce our size, the Roulettes easily deliver the best bang for buck.