I can bypass the VLAN security entirely by mapping the MAC address to my own ARP table. Is that correct?
Generally, no, you will not be able to do this.
Updating your arp table means that packets sent to the remote computer would make it as far as the switch. However, the switch still won't do anything with them, since your port on the switch is still part of a different network. With the arp update, the packets wouldn't even leave your computer. The update means packets can make it a little further down the road, but still won't reach the destination.
If you want to create an exception to a vlan membership, the best way I've seen to do it is with a layer-3 switch (so really it's a router now) at the core of your network that also supports ACLs (access control lists) for routing security. You set up this switch with a route between the two vlan's, have the ACL set up with a default deny rule, and add your exceptions as allow rules in front of the deny rule.