Yes, but as noted above it usually isn't practical. It adds extra variables, especially if measuring indoors. The two main issues are that 1) if measuring indoors, the distance to walls changes as you move the mic, and 2) you would have to be very careful to not change the distance from the microphone to the speaker as you move around the room, as that will affect the SPL level and though the shape of each off axis angle is unlikely to change much, it could misrepresent directivity (matters more if you are measuring at 1m than 2m, but still not ideal).
That said, I have moved the micr instead of the speaker on a couple of occasions where it was inconvenient to turn the speaker on its side for vertical measurements (side-firing woofers, for instance).
Based on your feedback:
1) Will be measuring outdoors, in a yard of 7x7 m2, and should be able to place the speaker higher that the surrounding walls, which are only 1.6m high.
2) Please see the following picture (the scale and measures are not properly represented, but i'm hopping this can represent well enough what i'm trying to describe):
1) The axis for the rotation will be the tweeter,
2) I should be able to elevate the speaker at about 1.8 from floor.
3) Distance from Microfone to the axis (tweeter), will be 2m,
4) Microfone placed in a stand, with a 0º angle to the axis, microfone at 1.8m pointing in a straight line to the axis (tweeter),
5) Microfone placed in a stand, with a 90º angle to the axis, microfone at 1.8m pointing in a straight line to the axis (tweeter),
For measurements, the stand would be moved in the exact angles from 0º to 180º with the mic pointing in a straight line to the axis (following the correspondent angle). If i'm understanding this correctly, this will ensure the same angles/distance between the speaker and microfone, as if we were rotating the speaker.
If the the above is true, i'm thinking in printing the circle with the angles in an acrylic sheet in real size, and use it to control the exact Mic/Stand placement. This would ensure that i would be able to align the Mic straight to the tweeter, ensuring the angles are being followed correctly.
Is the above valid, or my assumptions are incorrect?
Thank you in advance for looking into this!