Surely have to prioritise the Prem
If we were "in the hunt" for a SF, then yes.
We should (NB: "should" not "will") secure a home SF this weekend - 5 points from Newcastle at home, and we're uncatchable for 1st place with 3 Prem matches to go. Even if we lose to Newcastle, I think we're already guaranteed a SF of some description.
We're also 1 match away from a European final.
Reaching the European final adds 1 match to our schedule; but we ought to have 3 Prem matches where we can rotate to our heart's content.
Lose the Euro SF, and we've a nice little week off in there to rest up, which makes the balancing act easier; rest away, go hard at home, maybe start the usual benchers in the last round.
The sensible thing to maximise chances in the Prem would be to send the 2nd XV to Edinburgh, and just see how they do; and concentrate on the Prem.
But opportunities in Europe don't come along all that often, and if you find yourself in a SF there, you've kinda got to go for it.
ETA: Also worth noting that injuries are just starting to mount up a bit in the back 5.
Muir, Coka, Harris (and Bailey) all out of the back 3 (and Grace departed)
Lawrence and Ojomoh in the centres, whilst Redpath seems to be held together by K-tape at the moment
Not emergency stations, but something to take account of in terms of managing these last 7 weeks. 1 more injury here though, and we'll be dipping into the academy.
Russell (25) and Stuart (24) are both on course to exceed their 30 matches before the end of the season, let alone summer, which is less than ideal.
I'm sure that England/Lions will get them exempted if they want to.