Making transactions with non-DER-encoded (aka BER encoded) signatures non-standard has been on my TODO list for over a year now, but has never been the highest priority. That's the first step to making non-DER-encoded signatures completely illegal.
Note that if there is a core-dumping bug in OpenSSL's decoding code then it needs to get fixed in OpenSSL. Writing a BER decoder just for Bitcoin is a bad idea, it is much more likely our new code would have a crashing bug.