YOu call that a "minimal sewing" LOL!!!!! have not laughed so hard in a long time, and I can use a good laugh so it's fine.

My "minimal" has been my four thread Viking Huskylock serge and my Open arm (with table) Viking 990 that has the blind hem, buttonholer and all kinds of other stitches built in.

And with those two - I've sewed everything from very delicate lace/lingerie (it's remarkably good with slinky/stretchy PIA fabric) to very heavy duty things like replacing a zipper on a large old canvas tent (not the nylon ones like we have now days).

I always wanted to add a curved needle blindhemmer like I used in the Alterations shop and I always wanted a heavy duty steam iron (the kind that had a seperate water source).

For my "sewing" machines, I now have
1. Viking 990 that does just about everything, and I use is EXCEPT when I need a special purpose. It's not the best for FMQ and prefer not to stress the old gal with real heavy stuff anymore.
2. 15" Mid-arm Quilter, on the frame. This machine has no feed dogs so can't really be used for anything else.
3. Embroidery Machine.
4. Four thread Serge,
5. Singer 201 or 15, My husband would pick the 201, I'd pick the 15 if I could only have one, but that is because I like it better for FMQ - but it's a good, narrow feed straight stitch machine.

And because I can - but this is NOT minimal, this is "dream" setup.
6. Zigzag machine - where the bobbin and the needle move side to side as that gives a very nice satin stitch. And I do a lot of applique so having a dedicated satin stitch machine works well for me. So far this is my White 670, and it did a great job on the last project with involved 100 yds of ribbon satin stitched on the fabric (a set of 12 vestments for the Chapel at work).
7. Hemstitcher - because I've always wanted one
8. Blindhemmer (still on my wish list)

My husband is into the heavier stuff, so we also have a shoe repair/cobbler industrial - and for fun, it's treadle.

When I get machines moved out, I think I'll test ones and see if I can find a nice straight stitch machine for quilt piecing. However so far, my Viking feeds the best of anything I've tried, and with the needle side to side setting, I can easily get a 1/4" seam without changing feet.

Hey, you're talking to a guy who owns about 70 machines. 7 or 8 (or 9 or 10) seems really minimal to me! :)

So for me, minimally:

1. Zig-zag medium duty industrial
2. 5-thread coverstitch
3. 4-thread overlock
4. All-purpose zig-zag (including chain stitch feature, cams, built-in buttonhole, etc.)
5. Straight stitch
6. Free arm zig-zag

(2. and 3. could be combined in a single industrial machine.)

Possibly:

1. Straight stitch heavy duty industrial
2. Buttonhole machine (this is only out of curiosity and the coolness factor)
3. Embroidery machine (same)

If I had a minimal sewing studio, I would have to build a new building, about 40 x 80 or give up the man cave.[h=1]but if the big bomb went off.[/h] or I sucked it up, faced facts that I'll never use all these machines I stumble around daily

the list would be

2 home fashioned treadles, with a early 15 head and a 237 either can be electric

singer 16-188 electric but can be treadle
ww d12 treadle

singer 301, don't know why ..

at about this point there 'd be atleast 20 more that I would really need to keep. ya no.

The best buttonhole I've seen produced with these attachments was to mu surprise a Singer 190. Very basic, early 1960s and beige but it did it flawlessly. This was apparent when I went over the same hole twice and the second time it followed the holes made on the first run! I made another just to make sure and sure enough...
Conversely, someone else told me my swing needle 320k could do this just as well. I broke two (206x13) needles then gave up and will stick to straight stitch machines. The 320k can do a buttonhole but you need to write down stitch widths and do it all manually. Real pain. Easiest are the versions that use templates.

You have to play with the sewing machine settings to get the right pressures. The foot pressure usually needs to be increased a little, and the top tension decreased a little.

We should probably do a thread on vintage buttonhole attachments (if there isn't one already -- I haven't checked). The one that impresses me the most is the old Singer with metal coming out of it in all directions (#121795?). The result is really beautiful but there are no templates used. The Kenmore machines with the built-in driving lever are excellent. I've never had much luck with the Greist-type but I'm sure I'm doing it incorrectly.