SLS Block I will have about three and Block II five times more capacity in terms of payload mass to LEO, than any launcher which has been used for an interplanetary mission to date. But the mission doesn't seem more ambitious than Cassini. Is that a fair statement and if so why?
The instruments selected do not seem to make use of extra mass. There's no 2 meter mirror, not huge PV panels for a powerful radar, no landing probe or impactor. And not enough shielding to orbit Europa directly instead of Jupiter. Shouldn't they do something conceptually new with all the extra mass? Do they want to keep it within the capability of other launchers? Is it likely that two or more missions to the outer planets will be launched at the same time? 3 missions to Mars can do a conservative sample return, wouldn't it be possible with 3 simultaneous missions to Europa too?