911slf-
Yes, you're quite right. The outriggers are also for ground stability, if they had utilised a wing based main undercarriage then the outriggers would probably not be needed, but again the wings would need to be stiffer in order to hold the weight when on the ground without the fuselage scraping the ground, thicker in order to house the stowed u/c, etc etc.
As with most things in engineering, a solution is very very rarely the result of a single factor, it will always be the best compromise between all of the variables as you have elegantly pointed out
