Is it possible to process the impulse excitation using the constant Q transform (CAS Journal, Nov.93, p.1-4)?

The constant Q-transform is similar to one-fourth octave band smoothing of the frequency response. Please see the Smoothing section in the Plot->Plot Type Settings->Frequency Response /Spectrum… dialog box in on how to use this.

The other issues described in the above CAS Journal article are only valid for periodic signals, and not for an impulse response. Ideally the Q-transform is performed using time-windows of increasing size for low frequencies. This feature is not directly supported in WinMLS, but tests using time-windows of different sizes did not show significant improvement compared to using this smoothing method.