I haven't checked this forum for a while so have just seen this thread.
A quick (albeit belated) answer to the original question. Yes, it is possible to get to Bowen via Pineapple Ridge, however we found it less straightforward than the route via Warrawilla Creek. When we did it we had trouble finding a safe route down from Pineapple Peak to the ridge between there and the Bowen masif (north of the north saddle). Our group rule is that any one of the group can veto a route they feel is unsafe, so we ended up dropping down the west side of Pineapple Peak (very steep, dropped 250m for a 250m horizontal change in position) and making our way back up and approaching the north saddle from the west (this is the opposite side of Warrawilla Creek and since we didn't know the name of the creek we dubbed it Anti-Warrawilla Creek). This trip was done in the dry season immediately after cyclone Yassi and moving through this valley was very tough going. Much tougher than Warrawilla Creek which we descended via a few days later. If I did it again I'd avoid this approach and probably aim for a route towards the Prophet and then go up and over to approach the North Saddle from the ridge north of it. I hope that all makes sense...
In short, the route up Warrawilla is the most direct and 'easiest' route up Bowen (in my humble opinion). I've been to the summit on three separate trips (twice in one trip) plus have spent a bit of time going up (or attempting to go up) other peaks nearby.
As for Diamantina, I consider this peak a bit easier than Bowen. Access is via Diamantina creek so I wouldn't attempt during or after heavy rain. There is a point where the creek becomes too difficult to follow (just above a fork that heads left), leave the creek here and head left of the creek (at this point heading right is not an option as it is sheer rock face). The scrub is not too bad to get through. You might see some pink flagging tape tied high on some yakkas (from a September 2016 trip). At the top of Mount Daimantina is Daimantina rock (actually two rocks). Don't expect to climb either of these without ropes and fall protection. In between these rocks is a stainless steel canister with a log book.
I've attached a pic from the top of Diamantina rock (Mount Bowen is in the backgound).
I hope this is of some help.