Except that that's a linked list and not an array.

You can store your 'list items' in an array and still link to random items in the array - although an index instead of a pointer would make more sense in that case, but what else is an index than a pointer with fewer bits ;) The main advantage being that you don't need to alloc/free individual items.

Great, so now we're writing our own memory allocator?

If you want to call about 10 lines of trivial code a 'memory allocator', then yup, we're totally going to write our own 'memory allocator' ;)