Map object as custom field

Can i have custom field that will include different values like map works map<key,value>.

Imagine that i have a contract that requires 5 documents to be completed. This is one task/issue with qty of 5 and not 5 tasks.

If this is my main contract then can i have based on some change order a second value like changeOrder1=3

So imagine an object as:

ContractedQty:{
   mainContract:5,
   CO1:2,
   COX:4
} 

And also in some case to allow user to change it.

As you can imagine this is a project field and if you need to setup new values you should be able to update it from the fields.

In this case i could use it to have alternative field about complete work in the same way and have workflows that check that completed work does not go over contracted.