It seems the way you are thinking about it is backward. One should make the case that it safe to remove a DoS limit. Retaining it should be the default position. Especially as other limits are being lifted.
For instance, without a stack element size limit it could be possible to construct a Script which uses ~4GB of memory to validate by using the following Tapscript:
<396000 bytes push> OP_3DUP OP_3DUP .. OP_3DUP
With 333 OP_3DUPs this will create a stack with a thousand 3.96MB element, using about 3.96GB of memory just to store those. Of course there is more you could do, but a memory blowup is probably the most obvious example.
