As I've pointed out in a couple of tutes and articles I've had posted on forums and newsletters, you can easily knock up a simple 3V system more cheaply than doing BIAB in an electric urn with a tailor made bag so cost of entry isn't really the issue, and BIAB isn't an "entry" to AG with the inevitable progression to 3V or HERMs along the lines of "ideal first car but you will invariably progress to owning a BMW"
3v is a scaled down version of commercial Victorian Breweries because that's how beer was "always" made, and the reason for that was because it was the only practicable way of handling hundreds of gallons of product in a sensible fashion.
However at home, we only brew to typical lengths such as 23 L which doesn't require Steel's Mashers, steam cranes or tower breweries, so this gives us the freedom to use other methods that can produce beer without being slavishly attached to commercial style systems. As I posted in another thread we don't drive a cute little 1/3 model Kenworth Prime mover plus B double to pick up a bottle of milk at the Supermarket because that's how commercial road transport operates, we drive a Barina.
The reason that BIAB is often illogically perceived as an entry level system is that most current grain brewers are by historical accident 3v already and don't need to throw out their familiar and beloved kit and go BIAB, so BIABers tend almost exclusively to be new AG brewers. Rather than "entry level brewers" - to take examples of other new technologies in other fields, we could be more accurately described as "early adopters", like the people who initially bought Plasmas and LCD tvs whilst the mass still persisted with CRT boxes.
I've been PMing with one 3v brewer who is going to .. in his own words..."step up" to BIAB , and I also know a local brewer who is itching to get to a BIAB demo brew day so he can see if this can simplify his setup which actually has a lot of Blichmann gear etc... he just doesn't have the time to be doing 8 hour brew days and cleaning mounds of admittedly high end and blingy gear afterwards.
I'm surprised that there's still a lot of misapprehension about BIAB still out there - mostly from very experienced brewers even of the 'rank' of Graham Wheeler in the UK who just dismiss it - often condescendingly as "well we all know that BIAB is inferior and it will all blow over soon, and we can get back to running our mini-Victorian-tower breweries nudge wink" And of course gas will never yield to those silly new electric light bulbs and those will blow over as well. This year I think is a good opportunity to have a coordinated BIAB push during the forthcoming comp season and get some definite independent and not condescending runs on the board.. I'll be organising a bit of a task force and watch this space B)
end rant.
I think a ss conical would be really good with a couple of over the side immersion heaters. However following a failed no-chill-in-urn experiment that happened to me, I'd be wanting to use an immersion counterflow chiller to get the temp down, then oxygenate and pitch ASAP. A conical, especially if doing a big batch, is a poor surface to volume vessel for no chilling, my urn was still at around 37 degrees the next morning and by the time I could run it out into the fermenter and get to pitching temp some nasty had started breeding in it anyway. But as a one vessel system - provided cooling could be arranged - it should work just fine.
Edit: and because if you could afford a SS conical and were doing it because you liked BIAB and money were no object you could probably afford a glycol driven cooling system and could use that as an attemperator in the early part of fermentation as well.