I would have to go with Bill here. The simplest thing (and quite fast too) is to use the expander chip. My timings showed it works quite fast (especially if you use an SPI expander). For example, draw 96 characters of text in 54 ms. This is partly because you don't have to worry about generically setting individual bits, to send a byte of data to the LCD you simply SPI transfer that byte out, in itself quite a fast operation.
The library I wrote for the SPI/I2C expander supports multiple displays (link above). I doubt it supports all the stuff glcd does, but it may be enough for whatever you are trying to do.