Use of 「元」in honorifics

Question

While reading this bit of news, I noticed that the article used an interesting type of "honorific":

京都大学院薬学研究科の辻本豪三・元教授（５９）が医療機器販売会社（東京都世田谷区）から私的な旅行費用などの肩代わりを受けていた問題で [...]

Although the 元教授【もときょうじゅ】 fragment appears on its own elsewhere (for example in the title), it also follows every occurrence of the disgraced former professor's name (3 times in this short article), in what would seem to be the chosen honorific to address him.

My question(s) are then:

• Is the -元+[former address] form of honorific standard and commonly used? Would any former prime minister be 元総理大臣?

• Does the form carry any negative nuance? E.g would it be used in cases where the term/position ended normally? (in this instance, the professor obviously resigned in disgrace, but what if he had just been a retired professor)

• Any reason why the journalist would use this particular form rather than either a standard "civilian" -様 or the usual legal suffixes (-容疑者 etc)? (the insistence on pointing out his fall from grace seems a little petty to my untrained eye)

Answer 1

• As for the usage to avoid 呼び捨て, it is not common. It is the invention of the mass media. But there are even more unnatural ones. Ones (without 元) that are famous for their ad-hoc-ness are (草薙/稲垣)メンバー, 小泉タレント, 島田司会者.
• As for general usage, it does not have particularly negative nuance. It can be used for positions that ended normally.
• 様 is an honorific form and is not neutral. Although the writer wants to avoid dishonor, neither is there any particular reason to honor the person. A neutral one that can be used is 氏. 容疑者 can also be used, but if it is avoided, that is perhaps because the writer wants to be more specific, or is concerned that the majority of the readers are ignorant enough to not be able to distinguish 容疑者 and 犯人.