Don't have the time to do a redesign like I did for the Tour this time, but I think this outline would improve the race immeasurably:
Stage 1: ITT instead of TTT, possibly limit the distance to something like the 2015 Tour stage
Stage 2-7: don't need to be changed, perhaps beef up the Bilbao stage
Stage 8: finish on Les Praeres here. Villaviciosa is closer to Cistierna than La Pola Llaviana so no need to flip the stage starts too
Stage 9: Fancuaya with either San Lorenzo or Cruz de Linares before Marabio, which backs directly into the final climb.
Rest day
Stage 10: no change
Stage 11: if possible, HTF at Vela Blanca on the actual cape
Stage 12: queen stage. Salobreña - Sierra Nevada with Haza del Lino, Purche, then Sierra Nevada via Hazallanas and Sabinas
Stage 13: Martos - La Pandera
Stage 14: Montoro - Tomares with the 2017 finish
Stage 15: Sanlucar - Peñas Blancas with the finale indicated below
In any case, it seems like the Peñas Blancas stage will not be the first of the southern mountain block. The Estepona side is badly disconnected from other climbs, so it would be very lame if that's the MTF. However, there is a solution: first climb the Estepona side, preferably via the steep variant (the profile below as far as the pass)...
... then descend the
Jubrique side, before climbing the Genalguacil side to the finish. It's the profile below minus the first 1.1k. Finish can be either at the pass or at the end of the pavement, where the profile ends.
You barely avoid looping back on yourself this way.
Stage 16: Ronda - Montilla as planned for stage 13
Rest day
Stage 17: can't really improve it, unfortunately
Stage 18: finish on a proper side of Piornal like the one below, the steep section of which is the first climb of the actual stage
And/or this one, which joins the profile above halfway through the final false flat
In fact, you can just do the first profile, descend irregularly through Cabrero and Puerto del Rabanillo to the start of the second profile, climb it, then repeat the final ~2.5k of the first profile to the finish line. Again, not an especially complicated redesign.
Stage 19-21: no change