4km is for sure too far...
IMHO:
2 km could be nice compromise between telescopic view and realism...
Outside wiev as it is set atm is not realistic but it is nice to take fresh breath from outside of plane from time to time...
IMHO:
Leave it as is, but for some tasks just block outside view (for flatland tasks, those with less mountains, no pda (as u said) etc
120 min for start is too much, as those who can wait 2h - may have much better weather sometimes

IMHO:
45-60 min for start could be enough (also - don't make it same for all tasks - use it depend of task, flexible)
Mid-air collision recovery : allowed with penalty (symbolic)
IMHO:
-5 pts for Q using, sure u can be crashed by someone, but separation is the most important thing...

The briefing (a very light one) for 15 min
imho:
Briefing with weather don't need to be too precise and too accurate (yes! - may be wrong sometimes, as forecasts are) but hope some vital infos will be there (true or little wrong): those which can be easy known if u're on the ground before start, like => cloud coverage, more or less wind dir. (NNW etc), +- cloudbase alt, wind strenght: smthng like 'light wind', etc
Turnpoint helper range : 0 km
imho:
Set it to 1km 
During LLC those helpers was visible and turnopints was 90 degrees. Why not to make this one for tradition reasons?

my 2c
P.