Kind of a stretch, but I suppose there could be some potential for weak galvanic corrosion. Not nearly as much as steel with aluminum, and I think you could use a sacrificial fender washer between the brace and the strut tower at each bolt location if you were truly concerned.
When looking at the design there was an intent to make the bar into a helix but that sounded expensive and I feel as though I would lose the benefit of a strut tower brace. Decided to keep it simple and have the aesthetics be improved by the burning pattern.
Please post specs when you can. I'm really curious to know how much this weighs vs the stock pp one. Would the titanium be stronger or provide a ridigity benefit over the factory unit, or would weight savings be the primary benefit?
I doubt that this kind of brace sees much loading in the direction that would call for triangulating between the two main transverse elements.
I'm thinking along the lines of a simple Ti sheet between the two rails with a few lightening holes and maybe a "builder's logo" or even a customer's own personalized design cut out. Wouldn't have to be all that thick - guessing at dimensions, you could probably meet a width to thickness ratio of 100 with metal thinner than 16 gauge. Might well end up lighter overall, and it'd have to be simpler to fabricate than welding around all those small-circle 90° joints.