As stated above, the number of basebands in the array (of a given bandwidth) has a linear effect of the correlator. Eight baseband pairs would double the size of the correlator described in Memo 166.
On the other hand, increasing the number of baseband pairs, while keeping the total bandwidth constant, might actually make for a smaller correlator, as pointed out by L. D'Addario (1998, priv. comm.). For instance, switching from the current four 2 GHz baseband pairs, to eight 1 GHz baseband pairs, would to zeroth order halve the size of the correlator, because one could use half the number of lags to give the same spectral resolution (see §2.3). The most obvious argument against this is the difficulty of keeping consistent calibration between different basebands, particularly for single-dish data; this implies that the maximum bandwidth of a BB should roughly match the width of the broadest lines that would regularly be observed. Providing more narrow BBs would increase the number of BB converters and samplers, thus increasing the cost, but it would decrease the sampler rate, making them easier to design and build. There may be other problems with this scheme - the analogue correlator on the NRAO 12m, based on a similar idea, had many difficulties - but it should probably be thought about more seriously than it has been.