I don't want to dump Leon tomorrow, but if they did trade him and then find themselves with a need for another catcher in July, how hard would it be to find his replacement?
The nice thing about keeping Swihart as the 2nd catcher is that it would allow them to have a real 4th OF on the bench. As it stands, if one of the Bs has to come out of a game, they either have to put an non-OF out there or use JD there and lose the DH.
It is worth pointing out (again) that this team presently has three catchers on the 40-man roster and the guys slated to begin the year at Pawtucket and Portland don't exactly inspire a lot of confidence should they need to be selected to the roster. Unless the deal brings back a reasonable 3rd catcher who can be shuttled, I don't think the team can afford to trade or release any of the catchers right now. Even if that means "wasting" one of them on the end of the bench five out of every seven days.
I'm not a big fan of Dan Butler or anything, but I really don't think there's much of a difference between him and Leon other than the specter of Leon's 2016. They both have a solid defensive reputation and are well below average as hitters. Steamer and ZiPS have them both between a 69 and 76 wRC+ in 2018.
Leon AAA: .255/.343/.376/.720, 10 HR, 21 2B, 56 BB, 95 K in 498 PA
Butler AAA: .252/.335/.391/.726, 30 HR, 90 2B, 151 BB, 300 K in 1499 PA
Leon Minors: .238/.325/.330/.654, 24 HR, 92 2B, 253 BB, 404 K in 2319 PA
Butler Minors: .256/.347/.402/.749, 55 HR, 162 2B, 283 BB, 489 K in 2707 PA
I think Leon is utterly replaceable by Butler. If they get into the season and feel Swihart needs more ABs and can handle part-time C duties, I wouldn't have a problem with them moving Leon.