"Simpler" is surely something we could quantify, and while LOC tracks it loosely it's obviously not the same thing, and SSH is almost certainly more complex per LOC than typical. Where that becomes "much" simpler, and from there "much, much" simpler is fundamentally subjective, but if you want to put up some numbers based on some other metric feel free, and we can take this further; it strikes me as unlikely that a smaller system would fall in the range I would label "much, much simpler" - but I am not an expert on either piece of software.
Regardless, it is a digression. The complexity of openssh is not at issue, unless you are advocating they not use openssh at all. Nginx + openssh is absolutely unequivocally not "much, much simpler" than openssh.
Adding nginx interfacing with new, privileged code does add significant complexity that using-the-already-present-ssh does not. Some of this complexity is exposed to those who do not have any credentials. Therefore, the security of the system toward those attackers may go up for those reasons more than it goes down because of the existence of an additional set of root credentials they do not have easy access to. This is presuming that OVH's security is sufficiently trusted; a big assumption, to be sure.
We're still agreed that the best approach is some kind of reasonable hand-off of data from the privileged process that reads the data and the external access of whatever form, presuming any of the data really needs privileged access in the first place.
The reasoning you're using here about exposed attack surface and complexity is faulty. You are better off exposing a trivial interface with nginx or Apache than in giving someone SSH credentials.
"Simpler" is surely something we could quantify, and while LOC tracks it loosely it's obviously not the same thing, and SSH is almost certainly more complex per LOC than typical. Where that becomes "much" simpler, and from there "much, much" simpler is fundamentally subjective, but if you want to put up some numbers based on some other metric feel free, and we can take this further; it strikes me as unlikely that a smaller system would fall in the range I would label "much, much simpler" - but I am not an expert on either piece of software.
Regardless, it is a digression. The complexity of openssh is not at issue, unless you are advocating they not use openssh at all. Nginx + openssh is absolutely unequivocally not "much, much simpler" than openssh.
Adding nginx interfacing with new, privileged code does add significant complexity that using-the-already-present-ssh does not. Some of this complexity is exposed to those who do not have any credentials. Therefore, the security of the system toward those attackers may go up for those reasons more than it goes down because of the existence of an additional set of root credentials they do not have easy access to. This is presuming that OVH's security is sufficiently trusted; a big assumption, to be sure.
We're still agreed that the best approach is some kind of reasonable hand-off of data from the privileged process that reads the data and the external access of whatever form, presuming any of the data really needs privileged access in the first place.