There are circumstances where using the external camera (to look over walls or get a plan view of your surroundings) can be useful, and it is possible to fly/drive the SRV that way, the compromise is that you lose the scanner & other HUD elements. The HUD already provides most of the information that a 3rd person perspective would offer with the scanner giving a direction & rough distance to other local objects, and switches to a faux 3rd person view when landing.
So to initially solve a puzzle like raiding a base there are options, but fundamentally the game is designed to be played most effectively from the 1st person perspective.