Add companies to deal based on specific company property


One of my customers would like to be able to associate or at least add easily one or several companies to a deal that fit the requirements they need for that deal.

For example, they might need a company that works in a certain activity type to help them with the service they have to provide for that deal. If that's the case, they would like to be able to filter easily companies from the deal that fit the required criteria and then easily access the company selected based on criteria. 

So it wouldn't be an associated company as such but it would be a way to look for companies from a deal that fit all the criteria they want. They also want to associate/add several companies to one deal, which is currently not possible. 


Alternatives were for example create a dropdown menu custom property that would contain all the name of companies that fit a specific requirement (identified thanks to filters applied for companies) but this is really not ideal for them.