Good for you for thinking “outside the box” and going with a different yeast choice. I love both D80 and D254 for Syrah. D80 was isolated by the ICV in 1992 from the Côte Rôtie region of the Rhône Valley in France and is characterized, in my experience, by its big mouthfeel and licorice and spice flavors. It’s great for achieving that “minerality” character that I sometimes love in Rhône-style Syrahs. The only issue with D80 is that it tends to be a bit of a nutrient hog so make sure you are adding some kind of complex yeast nutrient to your fermentation to ensure there are enough micronutrients for this guy. It also has a fair alcohol tolerance, up to 16%.
D254 was also isolated in the Rhône Valley from a Syrah fermentation and has good alcohol tolerance — up to 16% as long as you give it appropriate air during the first half of fermentation. This yeast strain tends to yield more fruit-forward wines than D80 and so doing one lot with each and blending them together after fermentation is a really great idea for increasing complexity.
One thing I wouldn’t do, however, is blend the D80 and D254 yeast together in one fermentation. Believe it or not, yeast cells actually communicate to each other via chemical signals and they can be very competitive for resources (sugar, nutrients, oxygen, etc.). This means, that in microbial terms at least, they can get into little turf wars and the results can be ugly (think volatile acidity, acetaldehyde, and other off aromas and defects). Blending yeast cells is usually not a good idea because their competitive nature means that they just might not play nicely together. Myself, I just wouldn’t want to risk it. Is there any way that you can split up your Syrah into two smaller lots and ferment them each with one yeast strain and then blend those two lots post-fermentation? That sounds a lot safer to me.
As to using WineStix (sticks of oak in your wine after the fermentation is over), that’s great. If you don’t have access to barrels for your red wines, adding in oak pieces is a great way to go. There are many products on the market and it behooves any winemaker to experiment until they find what works for them and for their wines.
While I like your approach to adding oak alternatives during the aging period, don’t discount the positives that oak in the fermenter can bring, however. Fermenting on oak chips, dust, or even pure enological tannins can do a great many good things for red wines including improving the polymerization of tannins, helping to fix color, scavenge excess oxygen, and build structure early on. I personally ferment on about 1–2 g/L of untoasted oak dust or chips for most all of my red wines. The fermentation oak does not replace the oak that you need for aging later; it simply helps you build a better red wine foundation for further aging and development.