Greg – matters involving the relationships with the E/C aside, the splitting of the Strata Scheme as you originally suggested is in fact a Strata Sub-Division, that follows precisely the same process as would apply if a Developer has just completed construction of a residential building and then wanted register the complex under Strata Title.
Whilst the expense and degree of difficulty is governed largely by the number of Lots involved and the value of those (as determined for each by a qualified Valuer), if there are any “attachments” to those Lots (e.g. parking spaces), and how the Common Property is divided, there is an easier way.
Taking on board Jimmy’s suggestion about splitting the Strata and then having some overarching entity under a Community Title or similar, your O/C could apply to the responsible State Agency (Land and Property Information in NSW) for a “Subdivision of Lots only”, where as the name of the process infers, existing Strata Lots may be grouped together and Registered separately on the original Strata Tile, and with Common Property remaining with the O/C under that original Strata Title.
You can find some information on this less complex and less expensive process here – https://rgdirections.lpi.nsw.gov.au/strata_schemes/after_scheme_commenced/subdivision_of_lots_only but you would still need some degree of competent Legal assistance to proceed.