Sorry its taken a while to reply to your question, been frantically busy, This is very much a personal thing and will come down to what the client wants. What you will find with Ipe, is that it will weather very quickly, starting to lose its colour within a couple of months especially if the deck is south facing and exposed. If the client wishes to keep the fresh look of the timber then I would most certainly offer to oil it and for this I would choose D1 Pro as opposed to D1.
D1 Pro was specially developed for exotic hardwoods such as Ipe, Cumaru etc which are dense and difficult to penetrate. It has the penetrating qualities of D1 but with added UV filters, which not only help to keep the wood looking new longer but also enhance the natural reddish brown of woods such as Ipe. If oiling is chosen by the client then preparation of the wood is important to get the best from the finish and for this I would use Prepdeck followed by Net-trol. Due to the density of Ipe it is now suggested that new Ipe is treated with a 1 to 1 Prepdeck / water solution as opposed to the normal 1 to 4 mix. Using Prepdeck will have several benefits – it will remove any mill glaze, open the grain of the wood, wash out excess oils and degrease the surface of the wood – thus helping the oil to penetrate better and more easily. This should all be followed with Net-trol diluted 1 to 1 with fresh water to restore the woods colour – Prepdeck reacts with the tannins in the wood causing it to darken. Once preparation is complete and the wood allowed to dry for a couple of days then application of the oil can take place.
I would not recommend sanding the wood and then oiling. The issue with sanding is that while it may remove some of the mill glaze it will not fully open the pores of the Ipe especially if you do not use a coarse enough grit, nor will it remove any excess tannins or degrease the surface all of which will restrict the penetration of the D1 Pro into the Ipe.
I hope all of the above helps.