I suppose you could avoid the decreolization efforts of the 19th and 20th century. It would take a more decentralized Portuguese Empire where Macau would enjoy greater autonomy, but I do think it would be possible.
However, the most important factor is to limit Chinese immigration into the city. Patois can only be dominant if Macau has an Eurasian majority. This may be problematic, though, as having a very restrictive immigration policy doesn't seem very befiting of a city that is mainly intended to be a trade centre...