There is very little in way of cruelty in the character of Indiana Jones.  His pursuit of archaeological finds is fueled by a zealous love of the discipline.  He is not doing it for power or for personal wealth like his adversary, Rene Belloq.  I think that this might be one of the first areas of youthful and innocent qualities that can be explored.  Jones and Belloq are two preeminent scholars in their field.  They are both unrivaled, but Jones approaches the pursuit of archaeology with a purer heart, treating it as an end of itself.  This can be contrasted with Belloq, who treats it as a means to an end.  The ending would prove this as the opening of the Ark is disastrous to Belloq, but something whose force spares Indiana Jones.  The fact that the political backdrop is involved in this configuration is equally important.  Consistent with the Cold War vision of America as being pure of heart and pure of intent, Indiana Jones represents the freedom and innocent heart of America while Belloq works for the Nazis, which can be seen as the antithesis of innocence and youthful purity.  Another dimension that can be probed would be how Indiana Jones is able to utilize his guile, strength, and sense of mental dexterity to get out of trouble.  In this respect, he is very much youthful.  While he is extremely brave, his fear of snakes humanizes him, making him youthful in his approach.  His fighting style is not superhuman, but almost Tom Sawyer and Huck Finn.  For example, he is overmatched with the large Nazi thug and rather than fight him, he pretends to cower in fear (or cover his face from the impending disaster) as the Nazi plane propellers, miscalibrated by Marion, hacks up the thug in a gruesome manner.  In assessing the manner in which Jones gets in and out of troubling situations, there can be a undercurrent of the Romantic hero present.