You are absolutley correct it would be easy to beef it up, but I really don't think I'll have any issue with it. If it starts to show signs of stress cracks, then I'll weld it back up and add some reinforcmenet. I've never sheared a motor mount bolt, but I have ripped alot of motor mounts apart. I'd like to keep this one looking clean and simple so I'd rather not clutter it up with a gusset until it's proven that the extra stregth is actually needed. I really think it will be fine just like it is.
Thanks for the suggestion.