No, this is exactly what you’d have to do. You might even be able to downsample the graphics, though unless you’d have really clever software for this, the results will likely be less than pleasing.
There’s that too, but I mean the remaster of the actual 1985 BTI.
Some of those don’t look too bad (2 & 4 specifically). But yeah, in reality you’d lose some more of these colours.