There are a bunch of great ideas on youtube and Google for modular designs. I built mine to have removable sections and while I like it, it doesn't leave me many options for growth. I'd suggest doing something with more versatility like a rail system. Here's my bench.
And here is how the parts slide in and out.
The other thing I need way more of is shelving. Lots more shelving.
Here is where I stole the idea.
http://www.rifleshootermag.com/ammo/gun-loading-bench-strength/