The salary caps are fairly distorted by international top ups as it currently stands but if they are too exist as a competition leveling mechanism then they should be standardised across the comp (along with financial grants based on broadcast revenue). It is quite difficult to do with those top ups though, so it may never happen, at least not without significant carve outs that limit their effectiveness.
As far as knowing players from NZ in Australia and vice versa goes, a massive part of that is because of the separation. Standard fans know the players in their team and follow them, regardless of where they come from, open the flow of talent and the fans will pretty quickly come on board. It's not as though it would be a huge amount of talent would flow back and forth, but a few players here and there would help bridge the marketing gap and move the competition on from one too often seen as Australia vs New Zealand. You can see this pretty clearly in the NRL where kiwi players are spread across the comp and well known and liked by the fans of the teams they play for. The ultimate goal for this is not necessarily attracting more fans (though it improves the product which will in turn bring in more fans) but it's to help fans engage across the competition and outside of their home region - you don't think more people would turn out to see the Hurricanes v Force in Wellington if Jordie Barrett and Jordi Viljoen were turning out for the Force next year, even if they weren't playing any better than the last few?
That said, while I do think both these things would be good moves for the comp they're not strictly necessary for a cross over comp. They (or changes like them) become necessary if you're talking about a straight, 'merit based' qualification for that cross-over comp. While there are still these significant regional distortions impacting teams ability to preform and appeal to fans, there will need to be regional qualifications to effectively market and sell that competition to broadcasters. Otherwise the individual broadcasters will pay significantly less for the comp due to the risk it may not have any cut through in their market for a given year.