How about adding an option for adding decoy transactions?

Sometimes coinjoins can be picked apart just by looking at what adds up. This was painfully obvious on the darksend testnet the other day, as I remember seeing darksend transactions like Inputs: 500, 5 Outputs: 400, 100, 4, 1 where there's only one possible solution of who sent what.

One could easily construct decoy transactions to specifically add up to the amounts of the legit transaction. For example:
Intended transaction:
Input: 100
Output: 20, 80(change)
Decoy transaction:
Input: 500
Output: 10, 90, 50, 50, 35, 65, 95, 5, 100(all sent to change addresses)

If that decoy transaction is coinjoined with the intended transaction, there becomes 5 extra possibilities of where the 100 was sent to even if no transactions by others help mask it

Also, use more inputs than necessary, and use several change addresses instead of just one to help mask the intentions, and also having more and smaller outputs causes it to be more likely that they can be useful to help mask other transactions joined with them.