We all know that price had always had a desire to return to Missouri to reclaim the state for the south. I don't think Price realized that the situation had changes by 1864, and was not the same Missouri he left in 1861.

All military operation have first a primary objective and then secondary objective which are to be accomplished if possible. Obviously the primary objective was to take the war to the north, disrupt the union forces in Missouri and hopeful influence the presidential reelection of Lincoln.

Certainly one of those secondary objective was to recruit as many men as possible. Price probably saw this objective as a oppertunity to reconstitute the old Missouri State Guards of 1861. Like you said this was unrealistic.

But on the other hand had Price not become over aggressive in Missouri, and been able to organized such an army, he could have threatened Fredrick Steele's army at Little Rock by disrupting his main supply line, the Little Rock to Deval's Bluff railroad. Without this supply line secure Steele may have had to abandon Little Rock because of low water on the river.