I'm assuming this is the Fughetta op. 113; I don't know of another by him. I always liked this piece, because it is attractive, but also because texturally it is somewhat an outlier for Giuliani. Play it for people and ask them who they think is the composer, and they are more likely to grope around with names from an earlier era. But, when it is revealed to be Giuliani, it nevertheless does seem like his touch in this form.
In spite of all that, I somehow never got past reading through it a few times and adding it to my repertoire., much as I would have liked to have done. So, my commentary isn't from the standpoint of a well-versed hold upon it.
My copy of it is a scan withput any fingering, so, I don't know what fingerings you are looking at in your version by "JeffR".
For your measures 9 and 10-- I don't see any problem that would carry over from the second beat of 9 into 10. You don't have much of any option for fingering the closed position A major triad on the lower three strings; there wouldn't be any point to using a stretched configuration in the left hand that would deprive you of having the 2nd finger readily available for the low GT passing tone. So, I figure your question may have to do with the first beat of 9, and how best to move into the A major triad.
The only option at the beginning of the measure is whether to play the D open and locate the E on the fifth string, or to locate them in reverse string allocation, which would be the more intuitive response. If you use the open D fingering, I suppose then you might be obtaining the last sixteenth note B of this first beat with your 4th finger on the sixth string, and then sliding it down for the A on the next beat. If instead, you use the "D on fifth, E on fourth" fingering with your 4th and 1st fingers, then the most efficient technique that I can think of would be to lay the tip of the 1st finger down into an "internal bar" for the B at the end of the first beat, so that the fourth string E is covered, and then so is the low F# at measure 10, which you can "lever up" into onto the tip of the finger, so as to clear the fourth string open D. If that isn't your procedure, then maybe what you're running into is finding it awkward to have to jump the tip of the 1st finger from the fourth string E, to the fifth string B, and then to the sixth string F#. But I dunno if that is it.
In bar 37, I can see that it might seem a reasonable proposition to slide your 4th finger from the E at the end of m. 36 to the second string F# in 37. Again, I don't know how you are doing it, but, it might be more reasonable to move your 2nd finger from the 1st string G (to reiterate, my assumption) just before the upward move to the second string, and slide the _2nd_ up to the F#. This way, your 1st and 3rd fingers are readily available for the sixteenth notes B and C on the sixth string, and then you could stay up in that position and obtain the open voiced B major triad with the 1st, _4th_, and 2nd fingers on the sixth, third, and second strings.
As to your general proposition of the "sudden position changes"-- if that is a question as to viability as a techn ique, it's kinda hard to say it's either good or bad without considering each case. Suffice it to say that Julian Bream did this kind of thing ll the time, and he seems to have obtained some pretty good results. Your ultimate authority for doing so is your own, in that you "have the idea it makes for an interesting texture". It can, and does. But, like any technique, it has to be used intelligently. You have to decide if what you are doing is for the sake of the individual ephemeral moment at hand only, or does it it actually support the lines and phrasing of a gesture that has a shape in time? If a line is being fragmented by the disruption in tone color, then either reconsider the device, or, make sure that you can compensate in the right hand for the discrepancy. The measure 37 discussed above would be an example. The first beat E is a reiterated suspension, which resolves to the D# on the second beat. It's a considerable leap of tone color to transcend for the ear to capture the line moving from the bright open E to the much rounder sound of the mid-third string D#. Same thing for the second string F# connecting to the open E in the next measure. This doesn't mean it can't work. There is nothing "wrong" with a line, or lines modulating in tone color as they move. That can be an expressive device, and in the case of such as the resolution of a suspension, that expectation aroused in the ear compelling enough tp override the tone color discrepancy. But, you may still have to help it along.
Typed in haste; didn't have time to make it shorter. Hope it's clear without too many typos.