1.How can I change the icon for the .exe, including running the engine in window mode and on the task bar?
ResHacker.exe
It is not directly known whether the program effectively modifies icons for productions.
1a. Is that legal?
According to some user agreements, modifying the icon might seem to be a 'violation'.
However, if memory serves, and it often does not, JCL may have OKed that particular maneuver in one or more threads.
2. How do I display specific TEXT_STDOUT content only? i.e "Searching for Servers",launching .dlls files, but not the Conitec info?
TEXT_STDOUT is known, but not thoroughly.
Here, specific home grown functions are used to emulate stdout, or cout, to print multiple lines of debug info over entities or at specific positions and to diag output to the standard log file.
Some of those functions are freely available.
(New versions pending.)
3.How can I create .exe's specifically for -cl or -sv command line options, without resorting to bat files, shortcuts or similar?
Sorry, that is not directly known here.
4. Is all the above legal under A6 Pro? I believe it is.
1. see 1a.
2. The field of applicability seems askew for this item and the question.
3. This item was defined as a pseudo-direct unknown.
5. Is there a way to disable some command line options? for example -nc prevents the engine self checking for hacks; this is a risk for published games?
It is assumed that some command line options are for debug use only, and those options might not be accessible in the final production.
However, considering default mutability (no hacks), it seems a lean toward NO might be appropriate for that one.
The engine might not be known for its flexibility (but there's no need to cast pebbles and boulders...today).