Scribing plywood (Now with more RAD)

[lastlight]

So here's a problem I'm hoping the wood-gurus can help me out with.

Here is my stand currently. It is a flush-skinned box essentially. The walls are drywalled now too which complicates what I am considering here.:



Here is a tank I recently found on RC:



Rather than trim my stand I now want to scribe both horizontal and vertical lines into my plywood skin to create the effect of multiple pieces of wood. I only need to remove a saw-blade's width and about as much depth-wise. Maybe a bit deeper.

I thought about using a guide and setting my skill-saw blade to do this but I can't do the flat trim that meets the glass nor the edges of the plywood that touch drywall.

I also have a heavy duty utlity knife and I could score both sides of my scribe line and carefully go down the line scooping out the insides. Tough to get uniform depth this way tho.

Perhaps saw where possible and then do the edges with knife/patience lol?

Any ideas on how to do this? I require very straight and uniform lines or I'm not going to do it!

Thanks!