If The Sweeney film is a success...
...then they should remake The Professionals. If they get Christian Bale, Tom Hardy and Liam Neeson for Doyle, Bodie and Cowley respectively then it would pretty fvcking awesome. Or maybe even get Idris Elba to play Doyle simply because of his portrayal in Luther.
I'm not usually a fan of remakes but I think if The Sweeney ends up being a success then the next logical step would be to remake the The Professionals. Especially if you have actors like Bale, Hardy and Neeson as the three leads then people would watch it. The only problem is getting those actors to star because they'd all be focusing on their Hollywood careers.
Sic Parvis Magna 'Greatness from small beginnings'