So I'm collecting parts for a keg build too. Here are some of my thoughts.
Most of my gear now is tri clamp, 2" or 3" so that plays into some of my decisions.
Your first decision is right-side up or up-side down. You can use the original fitting to either attach the column, or flip it and use it as a drain. I'm setting mine up to mash so having a very low drain like that is my preference.
Wanting to mash in it as well as wanting to be able to get an arm into it to clean leads me to put a 6" tri-clamp portal on the bottom (now the top.) I picked up adapters to go from 6" to 3" to 2" so I can run any of my existing gear on there and if I need to get in to give it a good clean I can. It also means an opening big enough to dump grains through or stir during a mash.
For side ports, welding is the strongest option, but if you have DIY inclinations and access to the inside (like if you're cutting a hole for a 6" tri clamp anyway) pull-through tools are available for tri clamp and some NPT fittings. Not the easiest to work with but with a little sliver solder to follow up they are plenty functional.
https://www.brewhardware.com/product_p/ ... ool2tc.htm
If you can, I'd go tri clamp on the top. It'll serve you better in the long (or not so long) run. A spool to get you as high as you need to (possibly even just the sight glass, they are cool, don't let anyone tell you otherwise) then a couple elbows to a tri-clamp shotgun or adaptor to copper and a homemade liebig. That would keep the vapor path big as long as possible and let you swap parts at will.
Welcome to the wormhole. It seems like I'm always on the search for one or two more fittings... Glad tri-clamp is a standard!