multiple child records on a model

Yes Jack.  That would be great.   However I think thats going to run into some core SOQL limitations… 

You could however do this with 2 or more models linked with UI Only formula fields. 

So… create an account model. 
Then create contact aggregate models that count contacts, group by account,  and filter to only accounts in first model, and some field like “type”
In the account model add model lookup formula fields:   
    MODEL_LOOKUP(“ContactModel”,“CountId”,“AccountID”,{{Id}})

Rinse and repeat on the other type values to get counts of contacts by different types in your account data.   (Bye bye fomula fields…)

You might want to add a model condition to the account model so when it is requeried,  conditions are passed to the contact models and they get requieried.  You know,  keep it all in synch and don’t try to download all your records at the same time…

Fun…