Working around water supply to get correct slope from sink drain

[potterton1243]

I am replacing the galvanized pipe from my 50's master bathroom. When I demoed it, there was very little slope on the horizontal drain that ran into the wye. The issue is that there is a water supply smack dab where I need to connect the elbow. If I basically wrap the elbow around the water pipe, it is perfectly level going into the wye. What is the most straightforward away to get around this?

The things I have thought about so far is to drill in the middle of the joist and then use two elbows to drop it below the joists and connect the wye. Or maybe use a couple of 45s to do the same thing? Any help would be greatly appreciated!