Do Timelords Have Some Form of Control Over Their Regenerations?

When a Timelord regenerates there might be some influence on their part as to what form their next regeneration will take.  Let's look at this with the regenerations we've seen since the show's revival.

When 9th Doctor, Christopher Eccleston, regenerated into 10th Doctor, Davis Tennant, he was in love with Rose Tyler and perhaps wanted to be younger like her.  The next regeneration we see is the Master, who states, "If the Doctor can be young and strong then so can I" before regenerating into John Simm, who was younger and stronger than his Professor Yana persona.  We then witness the 10th Doctor's regeneration into 11th Doctor Matt Smith, at this point the Doctor feels old and weary and wonders if he has lived too long.  He regenerates into a younger, more carefree version of himself.

The Doctor comments that he could look like anything, have three heads or no arms perhaps, but yet every time we see any Timelord, they always look human.  Perhaps the Doctor will finally get his chance to be ginger.

Does The Doctor Need Companions?

We all see the Doctor dashing about the universe saving worlds and defeating monsters, but we don't see who he is at his core very much at all.  When we see him it's while he is "performing" for his companions and showing off a bit. You can see the school kid who just wants attention and to be liked in him at times.

But what happens when there is no audience?  How does the Doctor behave when there is nobody to impress?  We've seen the Doctor alone quite a bit at the end of David Tennant's run as the Doctor.  He gave an incredible amount of emotional depth to the character and part of that depth was the character's darkness.  Absolute power corrupts absolutely and we saw in The Waters of Mars what happens when the Doctor gives in to his arrogance.

The Doctor needs someone to humanize him and to ground him.  In The Runaway Bride Donna stops him from going too far and losing himself.  His friends and companions are his emotional compass and keep him grounded and from giving in to the possibility of things he could do but shouldn't.

The Doctor has ended his self imposed isolation and again travels with friends, yet still somewhere underneath there is a darkness that shows through occasionally.