Leadsled, according to the Distributor of the CH750, the RAA can register a factory built LSA with MTOW of 600kg.
The RAA can only register the same kit built LSA at 544kg.
Then there is the question of configuration. You cannot change anything at all on a factory built LSA without the manufacturers approval, which they may or may not, decide to give for purely commercial reasons. There is no onus on them to do anything at all. I doubt that a pilot can even maintain a factory built LSA.
As to what configurations are allowable in a kit built aircraft for registration in the experimental category, that is anyone's guess, but my assumption from reading Pprune and the total lack of hard facts available anywhere on the web, combined with CASA impenetrable regulations, leads me to suspect the worst.
The "worst" is that "It depends" on the individual CASA official involved, and that any determination is going to cost a lot of money and take a lot of time. More importantly, it would involve considerable investment in nervous energy in interacting with the powers that be.
To put it another way; the total lack of clear concise guidelines and the absolute lack of any authoritative voice willing to put their names to anything on this subject tells me everything I want to know.
To put it another way "ring XXXXXXXX at YYYYY and he'll put you right" is not an answer because it ain't official and of course it ain't in writing.
To put it yet another way. If I built a CH 750 with a Jabiru 3300, the larger Dynon EFIS plus Autopilot, shove an Airmaster Constant speed prop on it, do the fuel lines behind the firewall in metal to aircraft standards instead of rubber with a Three position fuel cock and fit a BRS chute, is CASA going to say "No worries Mate! Your good to go!"?