karma, the majority is not putting you in the 'bad guy' seat. No matter what you do, who you are, every decision you make, there will be at least one person who is not happy. Don't take it so personal. Don't have to be a gaping (_*_) on some things like I can be but it's not worth getting ruffled over, really it isn't.
Yes, if you are going to be roasting for a shop and your farmers market then YES, a 2 to 5K is a good starting point. Trust me, if someone orders 40 Lbs of coffee or you are doing 100 Lb a week, you do NOT want to be doing that in 1 to 2 lb increments. Remember, when you are roasting coffee, you really should *not* walk away from the thing while it is going. If only I would follow my own advice Id probably have had a few less fires in my Behmor, I claim old age / brain damage / CRS, whatever I can get away with for that
But on that, do the simple math and figure the time you will be spending in front of your machine. Now throw in wifey pooh, lack of attention, .. see where this can go? The faster you can be done with it, the better, honestly. That honey do list isn't going to complete itself hehe.
Another thing to consider, you want to develop roast profiles, yes that is good, but... The roast profile you develop in one machine is NOT necessarily going to fit on a different / bigger machine. In order to get a 'true' roast profile on a machine you need to roast in IT. Throw a smaller batch in to get an idea and tweak as you do more.
The Artisan I mentioned you can roast as little as half a pound at a time and up to 5 Lbs. I have heard some people say they can do almost 6 Lbs in it. Id say the type of beans plays a significant part of that, but that's a different topic.
If you already have that shop pretty much committed to buying coffee from you, Id say get the big machine, yes it's a chunk of change up front but you already have a 'money source' ie a sales path so it's not a shot in the dark, the income is already established pretty much.
Its something to think about.
Aaron