it doesnt need to be permanent just maybe elongate the time they come for. the reason y i like them on the wall is it was how they were shown in the second film, honoring an old tattered alliance when rohan were on their knees, i never liked how u could use the elves offensively because they would never help rohan if it wasnt in dire need
Actually, the Elves of Lothlórien never helped Rohan, at least not directly.
Not even the events of the First Age between the Wood Elves and the ancestors of the People of Rohan, or the Last Alliance (which Haldir generally relates to in the film) and the aid of Galadriel to Eorl could be seen as 'direct' involvements in War; the first two being anachronistic facts concerning Rohan, and the third being the display of power of one single sensational being.
As already and previously written, the arrival of the Galadhrim at the Battle of Helm's Deep is completely fictional; good, but fictional.
That's why, I think, a 'simple' (which is very significant and useful, after all) momentary summoning spell is more than enough.
Otherwise (given also the 'isolation' of the Golden Wood and the nature of its relationships with Rohan) another possible solution would be not lore accurate and incorrect (like the previous implementation of Radagast in Rohan).
P.S. A spell can be used in many ways; and, since we are talking about units, can (should) be used both for attack and defence, on Walls or on the ground.
Modifying a spell just for fitting a certain strategy would be a bit pointless, I guess.