You already have access to device pixels, you just have to calculate it yourself.
Anti-aliasing is not a good solution for orthogonal lines with low device pixel ratios like 1.25 or 1.5. which will be around for a long time. Browsers disagree with you - they don't use anti-aliasing for orthogonal measurements, they round. Which means they do in fact pixel-snap.
I agree that it can be misused like using device pixels for UI, but my suggestions makes the distinction more explicit.
Anti-aliasing is not a good solution for orthogonal lines with low device pixel ratios like 1.25 or 1.5. which will be around for a long time. Browsers disagree with you - they don't use anti-aliasing for orthogonal measurements, they round. Which means they do in fact pixel-snap.
I agree that it can be misused like using device pixels for UI, but my suggestions makes the distinction more explicit.