[Aiwendil]

To transport the picture in the fullest version we can get?

But if, as we agree, the fact that the tower was taken by assault is already inherent in GA, then I don't see how adding the sentence from QS makes the account any fuller.

If you really feel that adding the word "assault" from QS is critical, though, perhaps we could make the slightly smaller change:

RB-DB-32 <GA {and}And his hosts broke through and besieged the fortress of {Inglor}[Finrod], {Minnas-tirith}[Minas-Tirith] upon {Tolsirion}[Tol Sirion]. And this they took <QS by assault> after bitter fighting> for a dark cloud of fear fell upon those that defended it;

Some further comments, up to §149:

§144: Where QS has "And Morgoth came", GA has "Then Morgoth came", beginning a new paragraph. I would follow GA in this, both because it is later and because we have taken the fuller account of Fingolfin's challenge that immediately precedes it in GA.

. . . For I would see thy craven face.'
Then Morgoth came.> That was the last time in these wars that he passed the doors of his stronghold

We must guard against the danger of redundancy when we combine material from QS and GA. A small example is found here. In QS, when Fingolfin makes his challenge, he sounds his "horn"; in GA, it is here called a "silver horn". A few sentences later, QS mentions "the shrill music of the silver horn of Fingolfin". So in each text, the detail that the horn is silver occurs only once; however, since we take the first part of the paragraph from GA and the second part from QS, the detail shows up twice in our version as it stands, which seems superfluous. So I would remove the word "silver" at one of the two instances:

and sounding a challenge upon his {silver} horn he called Morgoth himself to come forth to combat

RB-DF-04: It seems to me that adding "withstood him" from GA is disruptive to the prose, since it separates the "it" (in "gleam[u]ing[\u] beneath it like a star") from its antecedent. I don't think the addition is valuable enough to warrant that kind of disruption (clearly, he withstands Morgoth in QS already), so I would leave it out.

§146: For a change, let me be the one to suggest an addition from to the text to provide more vivid detail! Here our text as it stands is straight from QS, but I would add something from GA:

. . . Yet {with his last and desperate stroke Fingolfin hewed the foot} <GA {I}in his last throe Fingolfin pinned the foot of his enemy to the earth> with Ringil, and the blood gushed forth black and smoking and filled the pits of Grond.

Here GA offers a detail lacking in QS (also, this more precise description obviates the erroneous impression I have seen people take from the passage, that Morgoth's foot was actually severed).

§147: In taking this section from QS, we miss the statement in GA that there was lamentation in Gondolin when Thorondor brought news of Fingolfin's fall, because many of the people were of Fingolfin's house. However, I fear it would be bad prose to say have "There was lamentation in Gondolin when . . ." followed, just a few sentences later, by "There was lamentation in Hithlum when . . .". Perhaps, then, we could justify combining the sentences, with some slight editorial work:

. . . There was lamentation in Hithlum when the fall of Fingolfin became known, and in Gondolin also <GA, for many of the people of the hidden city were Noldor of Fingolfin's house>; but Fingon took the kingship of the Noldor . . .