I do use the framerails as a lift point on the front end, (engine still in, auto gearbox out), without damage. For this i use a thick rubber block that is generously wider then the frame rails; its about 15x15x4 cm, about 7x7x1,5 inch. It's all about spreading the load. As first contact layer i use a t shirt.
View attachment 81947
No e9's were harmed during this lifting.
Regarding reinforcements; if you replace the front floors, then you can choose to remove the section that closes the frame rails, allowing access to the inside of the rails, and you can hammer/plannish the dents back.
You could weld in some stiffening ribs inside the frame rails, but it will make it harder to treat the insides adequately with rust preventative wax/paint whatever. And you cant really clean the welds well prior to sealing them So i have chosen to leave it all as per 'factory' design and to lift carefully in the future.