Please take a look at field model. You should not take any damage by running at moderate speeds over the grass. But you should need to run over tarmac/compacted soil to take off. At least with hvy planes.
Even if it were possible, which I doubt, you will be crashing with a lot of stuff/people in an airbase if you do not follow the runway.
Touchdown outside tarmac would have to be a lot less forgiving than it is today. In terms of both vertical and horizontal speed, it's totally different to land on a surface or on the other one (tarmac vs. grass). In the latter one, you most likely capsize with a slightly "hot" approach.
Finally....and again.... if this thing is "fixed", please take a carefull look at bomb damage and craters. If you have a useful runway, then bombing it would have some real effect. Make bomb blast and craters more realistic, both in terms of extension, graphic representation and time to repair... (still missing Malta Scenario approach to buff job)
Cheers,
Pepe
[edit: my grammar sucks
]
