If there is obviously a need for such a book - wouldn't the Rebbe have seen and realized the necessity for such a book to be published way back then!?
Barring no other logical explanation, (which, I would certainly eagerly welcome,) I guess that Mrs. Tauger & Kehos don't share the same perspective of the Ohel as that of the Rebbe.
As no one else has offered an explanation - I would offer this answer; Essentially, your question is a valid one. The reason the Rebbe never requested Kehos publish this type of book is because the Rebbe did not put emphasis on the Frierdiker Rebbe's tzion or histalkus to be greater than that of 770.
By the Rebbe - this was just one of many inyonim that are connected with the frierdiker Rebbe. But the eikar - the main focal point is 770, and not an inyan of a tzion, or a histalkus or a kevurah, or anything connected with an aspect that Chas V'Sholom - the frierdiker Rebbe is no longer connected with the gashmiusdiker world AS WE KNOW IT.
This explains why there were no books published or cafe's, social halls/clubs, cheders, shuls, tents, etc. etc. built or erected near the ohel of the frierdiker Rebbe - BECAUSE THE REBBE WOULD NEVER WANT IT OR ALLOW IT!!! - This (ie-the Ohel, histalkus, tzion etc.) IS NOT THE EIKAR!!
Fast forward to present day “Chabad” - and we find an array of books & publications solely dedicated to portray and illustrate the Rebbe in the EXACT OPPOSITE of how HE HIMSELF would portray & illustrate the Frierdiker Rebbe!?
I leave the conclusion for those who are not intellectually and emotionally challenged to figure it out for themselves. (Additionally, one may study the sichos of Yud Bais Tammuz 5745-1985 for additional points I may have left out.)