I think one of the most useful features to add to the trainer would be a "No knockback" option. When enabled, missiles would no longer throw you back. So annoying, being blasted away every two seconds.
i did it the intended way between those two skyscrapers. was really challenging and a little frustrating, but in the end i did it! =)
all thats left now is to find all those collectibles. i have 118 of the landscape ones and about 38 or so of the hints. but i don't exactly know which ones i already have. so i guess i have to visit all 250 places on the map . . .
btw. there is this guy "roosterteeth" at youtube who is assembling a walkthrough for those collectibles. the first 14 are in his first video. good thing is, that he explains where they are found and you have the video. makes it easy to follow. but i guess those 14 don't help me very much since i have most of em. ~=)
i hope he completes all 50 of those and the 200 of the landscape collectibles! =)
[EDIT] i just had some more ideas for trainer functions. 1. never detected (i sometimes just want to beat up infected without being bothered by the military!) 2. no cooldown time/heat up (i'm not very patient sometimes, and don't want to wait until the tank feels like shooting another round) 3. invincible military/infected (making some of the events a lot easier. sometimes i get the feeling that neither the military nor the infected are able to care for themselves!)