Sanke keg project?

[Thedutchtouch]

So.. I have a 15.5 gal standard sanke keg. I currently am doing BIAB on the stovetop in a 10 gallon bayou classic which currently has no drain. I will be purchasing a propane burner soon, but eventually plan to have a Brutus 10 w/HERMS system. My question is this-which vessel would make the most sense to build first, HTL, MT, or BK?
HLT: arguably the hardest to build, will have the HERMS coil, drain valve, sight glass, and thermometer
MT: false bottom, drain with pickup tube, return for herms/vorlauf, thermometer
BK: drain with pickup tube, sight glass, thermometer.

So which one to build first? Or should I just keep it on the shelf for now until I can find two more and do them all at once? I was thinking Mash Tun, as I also have a 5 gal cooler but don't want to modify it into a MT as it's a bit small. I could heat the strike water to temp in my pot, pour it into the keg MT, while mash is going heat sparge water in pot and dump it into 5 gal cooler. Then use pot as BK. Obviously this wouldn't be a HERMS system yet, but seems like the quickest way to get to a 3 vessel system without buying pots or coolers that I won't need down the road. What do you all think, got any different ideas? Thanks in advance for any thoughts/suggestions.

 

[rgauthier20420]

I would advice to do a bottom drain mash tun with the keg first. Insulate it with some water heater insulation and get the bottom drain kit from brewhardware. You've got a big enough kettle to boil for 5 gallons batches safely and your idea of keeping your 5 gallons of sparge water in the cooler will work for now.

As a side note, I'm completing my RIMS and e-panel this week hopefully and I might be getting rid of a 3rd already cut and drilled keggle if my no-sparge tests go ok on efficiency. So, you may be close to getting your 2nd keggle if you'd like

 

[Thedutchtouch]

No bottom drain for me. While I like it, I plan to cut the top skirts of all 3 keggles, leaving the handles in place like this (I'll leave a small tab to mount the sight glass or mount it close to the handle) https://www.homebrewtalk.com/f11/how-lighten-your-sanke-keggle-214694/ . Having 3 matching kegs matters more to me than the slight upgrade from bottom drain to side drain w/pickup tube.

 

[Rivenin]

if you want it easier to build... have a removable herms, ala wort chiller style.