For the changes you need it is not worth saving and modifying. It will cost more money to do them versus a new vanity. With the with of 59" You can do 3 cabinets, 2 fillers, toe kick, and touch up kit. You can do...from left to right.

1 - 1" filler

1 - Vanity Sink Base 24" W

1 - 9" Pull Out Cabinet

1 - Vanity Sink Base 24" W

1 - 1" Filler

Use toe kick to cover bottom.

It will be tight but it can be done.

You will also have to add plumbing to add new sink.

Most bath vanities are now 34 1/2" tall standard now, which will also solve the 30" issue as well.

Filipe Custom Woodwork breaks it down nicely. I would think twice about adding a second sink since you'd be left with only under sink cabinets + the 9" of pull out (my personal preference is lots of counter top + drawer storage)

Maybe something like the HEMNES 56" double vanity could work (has very nice drawer storage =)