That would require months of development work and core changes to the game’s backend systems, most notably how saving progress functions.
Months? Months? Not in this universe, or any other.
Do you think multiple routines of the
same code checking server status, saving, retrieving and cross checking the save game data are spread willy-nilly throughout the code, just dumped in again and again where necessary?
No, there will be a set of functions, all relatively close to one another, which will handle that sort of stuff and can be called upon from anywhere in the rest of the code. Grouping code into functions that can be called upon from multiple places and reused not only makes the code smaller but helps to keep code organised. However the real utility of these re-usable functions is that, because all the code for a given purpose is all in one place and re-usable, you're reducing the locations of points of failure (bugs) and, more importantly, if you need to make any changes you only need to do it once.
The point is, all retrieving of data from online and local storage will be handled in one place, so PD's coder(s) can just go to that one function and remove (or comment out) any lines specific to online storage and the cross-checking of online/local data. Similarly for storing data, any references to saving online can be removed (or commented out) with ease. Then it would be a simple matter of permanently hard-coding certain variables to deny access (disable interface items) to certain parts of the game that absolutely rely on being online; so that would be Sport Mode, Lobby, Discover, The livery editor and parts of the Library).
I can assure you, that sort of stuff is absolute childs play, menial, do-it-with-eyes-closed level basics... managing file i/o is probably the third thing most coders learn after "hello world". Setting variables would be the second.
If experienced hackers can take the binary file(s) of a program with copy/security/licencing protections, disassemble it (into Assembler language... which is a million times harder to understand than (normal) human-readable source code) and remove said copy/security/licencing protections in a matter of days of a programs release then I'm fairly certain - no, I'm 100% certain - that PD's coders, with access to their
own source code, can comment out a few lines in a matter of hours. Hell, give me the source code, and a dev-box, and I'm sure even I could figure it out within a day or two.