What if Germany had scrapped the Schlieffen Plan and instead focused on holding Alsace-Lorraine from the French, as well as attained little Russian territory purely for defensive reasons? I am not suggesting a full-scale invasion of Russia, since that's the last thing the Germans want, but a purely defensive position in hopes of supporting Austria-Hungary and not upsetting the British for disrupting the balance of power.
^ this previous answer I've given should be pertinent
instead focused on holding Alsace-Lorraine from the French, as well as attained little Russian territory purely for defensive reasons?
This certainly was a possibility; prior to 1913, Germany had 4 mobilization plans, each one of them essentially a modified derivative of Schlieffen's 1905-06 Memoranda. Aufmarsch West I & II envisioned mobilizing for a one front and two front war against France/France and Russia respectively, while Aufmarsch Ost I & II envisioned one front and two front wars against Russia/Russia & France respectively. On top of this, Kaiser Wilhelm did have a personal crisis just before the invasion of Luxembourg, and requested that Moltke focus against Russia instead, so it's not as though it was impossible.
Such a plan had advantages; it would enable the Germans to support their Austro-Hungarian ally, of whom it had been recognized before the war that it was militarily in poor shape. They could focus the bulk of their armies and try to smash the Russians in the salient of Congress Poland.
At the same time, the French would be in a difficult position, as the war would then be confined to Eastern Europe, a spat over Serbia in which Germany could hypothetically defend it's actions as in it's own defense and that of it's ally. At the same time, meetings of the British cabinet in late July made it clear that unless the Germans took the drastic step of invading Belgium, the chances of Britain entering the war were minimal. Jean-Jacques Becker's social history of reaction to the war in France, 1914, How the French Entered the War, seems to indicate that France's civilian population was not keen on going to war over Serbia. It's also doubtful that France's largely left-wing/socialist Chamber of Deputies at the time would have supported this either, and Viviani curtailed Joffre's efforts at an earlier and more forceful response to the July Crisis. So it's unlikely that Britain would have been involved, and equally so with France. Even if France did enter, Plan XVII (France's only war plan) centered on a German invasion of Luxembourg and Southern Belgium, with two French armies pushing into Alsace-Lorraine to outflank it from the south, and three armies stationed further north to parry and reverse the German thrust (though Joffre modified this last second to include an attack into northern Lorraine, aimed at the area where ultimately the 4th and 5th German Armies were. So French plans would have been hampered by lack of a German attack in the West, and attacking through Belgium and Luxembourg would have likely precluded British support.
Although:
I am not suggesting a full-scale invasion of Russia, since that's the last thing the Germans want
This would be a difficulty; for one thing, the Austrian and German militaries, along with most of those of the major powers, were very much wedded to Offensive strategies/operations. Firepower was recognized as making tactical offense difficult, so there fore strategies (more what we would call operations today) were centered on bringing to bear a large enough force, with as much firepower as possible, at a decisive point. German military thought, especially in the wake of Schlieffen, emphasized a decisive battle, such as Sadowa in 1866, or more precisely, a 'battle of annihilation' like Cannae or Sedan (1870).
Since 1912 at least, with the Scutari and Algeciras Crises, the December 8th Imperial German War council, and the announcement of the Russian Great Programme that year, war in then future with the Entente was seen as more or less inevitable, with Russia as the 'big bad'. Russia had to be portrayed as the enemy, and thus needed to appear aggressive, so as to gain the support of the SDP, which had been lacking when war with France was threatened in 1912. But this meant a war with the Entente as a whole, as the General Staff assumed France would support Russia, thus taking for granted a two front war. The result of this view was Moltke's discontinuing of the updating of the eastern deployment plans in 1913, with the view being that going after Russia first would mean contending with the same issues as Napoleon: Russia's immense manpower and strategic depth. Therefore, the view was taken that France was the weakest link, and so a concentration in the West was the deployment that promised the greatest amount of success. To this must also be considered the paranoia of German leadership about 'encirclement', and the so-called 'military culture' of the German Army, which developed in the wake of 1871 with a move towards increasingly more ambitious aims at annihilating the enemy (Vernichtungsgedanke). Germany was 'surrounded' by enemies, therefore those enemies must be destroyed to secure German 'development', and fighting them piecemeal wasn't going to do it.
It is, however, debatable the extent to which German war plans were solely predicated on a short war, as I discuss [here] (https://www.reddit.com/r/AskHistorians/comments/3bl50d/was_there_any_way_that_europeans_in_1914_could/). Moltke, along with some other German military men, was pessimistic of the prospects of their plans. For one thin, he seemed to assume Britain's involvement, hence the decision to leave out the attack through Maastricht, thus keeping the Netherlands as a 'windpipe'. He also strengthened the left flank, so as to protect the route into the Saarland and thus safeguard German industry there.
TL;DR: focusing on Russia was sensible, and had advantages, but also disadvantages; moreover, the army was pretty well set on it's plan of attack by 1913-14
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Hope all this helps!