I am not a scholar but I think that this is an Islamic tradition that every temporary Custodian of the Holy Sites have practiced past and present. It is not something that I have noticed before/put emphasis on but I understand why it could be controversial.
I suggest asking well-known Islamic scholars who will be able to answer such questions in detail on well-known websites. I encourage you to contact scholars in KSA as well and institutions. For instance the Islamic University of Madinah.
See this reply for all it is worth in the meantime:
Q-1: IT SEEMS THAT THE KING OF SAUDI ARABIA`S NAME IS ENGRAVED ON THE DOOR OF KAABA AND A PHOTOGRAPH WAS SHOWN TO ME,BUT I WAS UNABLE TO READ IT DUE TO THE ARABIC CALIGRAPHY.IS IT BECAUSE THE KING IS THE CUSTODIAN OF THE TWO HOLY MOSQUES,A RITUAL TO DO SO FROM EARLIER DAYS OR IS IT REALLY WRONG TO DO ITAND IS HARAM.PLEASE ENLIGHTEN US ON THIS.
It is indeed true that the name of some of the kings of Saudi Arabia are indeed engraved on the bottom part of the main door of the Holy Kaaba. One cannot say doing such a thing is haraam or forbidden, as there is no such specific restriction prescribed in the Quran or the Sunnah. Beloved brother, these people and their families have declared themselves to be the custodians of the Holy Mosque, they build and maintain it to the best of their ability, and since they are kings of this world, for a time period decreed, they may do as they please!
The Holy Kaaba will remain the Holy Kaaba and the Sacred House of the Lord of the Worlds; whether one who builds and maintains it writes his name on it or not! If the people who built it wish that their name should be remembered by fellow man and history, they will obviously make sure that their name is engraved on it; and if they wish to get their reward from The One and Only King of kings, whether they write their names on it or not, they will have their due reward from Him.
Source: (I don't know the affiliation of that website but it seems not to have any ties to KSA at all)
http://islamhelpline.net/answer/461...rabia-s-name-is-engraved-on-the-door-of-kaaba
Related thread:
https://english.alarabiya.net/en/variety/2018/12/26/Oldest-out-of-six-Kaaba-doors-tours-the-world
Although I am not a scholar, my humble opinion, makes me inclined to your viewpoint but I don't think it is haram at all.
Speaking about keys (brother, I agree with everything you wrote earlier, so I have not replied again, also because I was busy updating 2 threads and now I saw this thread, just wanted to give you a notice instead of writing a short reply - I might write a long reply tomorrow as it is very late but the unnatural coronavirus times have paralyzed normal life) this video might interest people.
It contains English subtitles.