Im ok with 20% Strength penalty, maybe can be raised to 25%, but not more. Bonus for have more than the required strength is not needed.
I think weapon handling need a nerf, it gives 3 special points for most builds. It should give 2 ST points, or have a minimum ST requirement of 3-4
The EN part was suggested before, and i think that can be good to improve the medic role because it will give more chances to "resurrect" unconsciousness people. i think 5*EN should determine the amount of negative hp a char could get before dying.
CH suggestion sounds interesting to improve this atribute. But it may require some changes in the protection system to not be abused.
I think low luck should increase the chance of a critical miss. i dont know what is the base chance of critical miss but it may give: base-3+LK/2. So a 1-2 LK char will have 2% more chance for critical misses and a 9-10 LK char will have 2% less chance.
Low IN chars should have some limitations, but the hinkley IN requirement would be removed (it can be bypassed anyway if a friend ask for the weapons for you)