Why a lid at all on boil keggle?

I am getting ready to cut the top off my keg to be used as a boil pot. I like the look of the keggles with the tops completely open (no rim to set lid on). From reading the forum it sounds like opening it all the way up also simplifies cleaning.

Experienced folks, am I making a mistake if I cut the top all the way out and grind it down smooth to the keg wall to allow total access? Or should I leave a lip to set a lid on? I see most of the folks only cut a 11.5-12" hole and leave a lip. But whenever I have seen them being used the lids are not on the boil keggles.

If have access to the tools, given what you know would you open it all the way up or leave a lip for a lid?

I think covering the top with a lid helps the water heat up faster?

My kettle doubles as my HLT (for the moment). That's the only time I use a lid on that kettle.

You want a lid option for a few things.

1. During cooler/colder months it will be easier to get up to a boil with the lid on. Even in the summer time, the lid helps. Basically, you're containing the temperature within the keggle until you hit boil.
2. Keeps things out. Such as bugs, leaves, things crawling or flying through the air. Stray bird poop too.

We take the lids off during the boil so that the steam will escape. Otherwise you won't get much of a reduction during the boil.

I have a ~12" opening on my boil keggle, and have a nice SS lid that fits it. Works out really well with the items mentioned above.

I put the lid on to get to a boil faster, remove it during the boil to free the escaping dms and then return the lid to keep out contamination when whirlpooling/cooling.

The other thing to consider, although harder to find than a 12 inch lid, is to cut the top all the way off and find a 16 inch lid to fit that. It certainly would be easier to clean and weigh less with the whole top cut off. Only other issue I see with this route is if you are going to be pushing it with volumes, that extra lip helps with boil-overs etc. That and slightly less durable if it were to take a fall hitting that top lip.

Yeah, the top [rounded edge] of the keggle isn't as bad as hitting a 1.3mm thick sheet of stainless steel.

Personally, I got the largest lid I could fit through the upper opening of the keggle (the rounded over part). Simply cut the hole so that the lid works well and you're pretty much set.

It is not necessarily needed but as said it speeds up boiling and prevents contamination after boil.
On my HERMS I got one lid for MLT/BK, when I am mashing it is on MLT and when I'm heating wort it is on BK. So if you put it this way you don't need it for BK but you'll want it for MLT.. either way you can use it for both.

I use the top I cut off the BK for the MLT cover/lid (I put a solid TC cap over the opening). I then have an actual lid/cover for the BK. So, I only bought one lid for these. I'm also going to use a lid I've had on hand (for some time) for the HLT. Just need to get that finished (turning a short pony keg into the HLT) before my next brew day.

The only time I use my lid on my brew kettle is while I'm storing it. It's keeps the dust out.