That makes a lot of sense. The story certainly suggests that initially the Doctor is acting strangely because of the machine, but later hints that actually he had a plan which he may (or may not) have communicated to Peri, so it is really difficult to work out what can be attributed to the machine, what might be attributable to the machine but is being exaggerated, and what might be part of a plan whose existence the presentation is attempting to conceal. I certainly got no hint that the idea was that he had been influenced by Yrcanos - I'm sure if Colin Baker had known he would have had immense fun immitating Brian Blessed.

It also sort of makes sense that it was JNT who grafted in the not-actually happy ending, even allowing for the fact that 4 or so years earlier he'd been content to allow Adric to be bumped off but of course a) Adric was male and b) JNT was on good terms with Saward at the time.