They could make the panels structural
If instead of having a roof deck with underlayment on top of it, shingles/tiles on top of the underlayment and solar panels top of the shingles, we had a roof deck with solar panels top of it, skipping the underlayment and shingles by filling their role of keeping water off the roof deck, overall installation cost would be significantly reduced, especially in new construction.
Not sure that really helps all that much with the aesthetics, you either think tinted glass looks good on a roof or you don't, but it solves a more important problem since installation cost is a bigger and bigger factor as solar panels get less and less expensive. And hey, maybe solar panels look better if they are lapped like shingles - you could even have the option of using ones of different tint to get that mixed shading popular in shingles.
You already have to replace shingles every 20-30 years, which by a nice coincidence is about the life expectancy for solar panels (barring hail, which would trigger the replacement of either shingles or solar panels) Sure, tiles and slate last far longer, but they are also more expensive and there's little point to having a more expensive roof if you are going to cover it up with solar panels anyway.