why not just (SPOILERS)
sell the shop pack up and leave. Give the money to Mable and move on? I don't think its disclosed how much he gets from the Lafontaine family, but he would have gotten a sizeable chiunk selling all the materials ect? why risk it on an insanely convoluted plan that relied on having both Richie in Francis there, then one of them leaving (giving him time to lay the seeds of distrust) then return so they could hopefully kill echother and not just blame the old man.
Unless his intention is to take out gangsters. but Roy seems to be overall fairly decent, yes eh killed people but he was well liked in the community (according to others) and according to Leonard is the one who gave him his start and got his business going at first.
the whole Leonard being a former gangster is dumb imo. All he had to be was an experienced ww1 vet, on the front at first then let's say moved into counter intelligence (explaining his string pulling abilities).
I almost laughed out loud when he started showing his horrible tattoos that may be period accurate, but looked like a small child had doodled them on. the film almost jumped the shark imo