What to do with a Schultz Petal Table Base (Missing Petals)?  

If you don't like the top/base marriage, definitely sell the top.
It presumably has had mounting holes drilled into its underside for attachment to the Schultz base. I don't know how much that will affect the price, especially if the holes will be visible when the top is mounted on a tulip base, but those wooden tulip tops start out REALLY expensive, so you'll probably do well regardless.
I've never seen a complete used set of Schultz dining-table petals for sale, so I think your only choices are to buy new petals from Knoll or have them made. If you need a template, you might have better luck buying an individual petal from Knoll in white polyurethane rather than teak.

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If you get them made in redwood, it would probably be worthwhile to make sure that vertical grain boards are used as that is both true to the original design, and was done for "structural" reasons. Wood is harder perpendicular to the growth rings (and redwood is very soft, so this makes a difference), and it will be less prone to cupping.

I can supply pic
of original redwood petals if you want some for reference as needed.
I will post pics of my post refinish of my petal table shortly. I think the leaves turned out pretty nicely.

I'd love to see your table.
What did you end up using for finish?
To the OP: Price replacements from Knoll first. Having accurate repros made won't be inexpensive.

I'm not sure
where the redwood suggestion came from -- but Leif is correct. Better yet, avoid soft woods like redwood altogether. (Doug fir and some pines are harder than redwood available today, and would be preferable, if a softwood is desired.)

as I understand
the first ver of this table was equipped with redwood leaves as it was intended for outdoor use (while soft, redwood is very bug and rot resistant)

Yes the redwood suggestion
Is because that would restore the table to its original self. And the particular way they used the redwood is an important detail in that..
If I had the table I would restore it with redwood, bearing in mind the to make the petals out of vertical grain boards (quarter sawn). I imagine the petals on the originals were edge joined from multiple pieces of wood not on single wide piece, so you could pick through the redwood lumber in any big box hardware store in the USA to get it. If you need petal-width quarter sawn redwood that might be very hard to find indeed.
If you just wanted to improve the table as opposed to restoring it, teak would be an ideal choice.

I'll do a pic
tomorrow. but the redwood petals are from single slabs. First rate lumber all around

Wow!
Well then. Finding redwood you can re-mill and glue up into edge grain petals is not too difficult. Finding slabs of quartersawn redwood will be a lot harder. Google will turn up something. Salvage logs or something.

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I'd like to see a snappy of the petal base with the tulip rosewood top. Perhaps it's a desirable marriage, as is?
Why not?
Best,
Aunt Mark

pics and musings
this was quite an undertaking and I am not sure where I am on the whole process.
- Top was ugly. Clouded. Had my carpenter buddy plane it down 1/64" (approx) each and then sanded the rest.
- Went at it with Tung oil for tone and protection and then a light Danish Oil like finish to seal it (both from my local furniture restoration guys whom I really trust)
- Base is pretty decent. Just cleaned it up with a toothbrush and toothpaste.
- ONE PETAL had obviously been knocked off at some point and sloppily glued on (and sloppily drilled out and sloppily pegged). We had to pry it off. I filled the damage underneath with good quality wood fill (that will take a screw). Now it is ready to re-mount.
I am considering stopping right there. I COULD round the edges. I COULD clean up the sides and bottoms (still drips/streaks from sloppy earlier work). I COULD stain the wood fill to match....I COULD sand/paint some of the dings on the base, but I don't think I will
I will probably sell this and whomever buys it will have to/want to put some work into it. The base issues are honest and not distracting, so I would consider leaving them as is. The leaves are LOVELY now, look right, and importantly, are LEVEL probably for the first time in 50 years. You cannot see the sloppy undersides, but they are there and if the buyer wanted to do something? Not a hard job.
It's that old balance of what to address and what to leave along. I think I did alright as the top needed to be addressed at some point, I had the tools and skill set and now you can see just how lovely this baby is.
She's a looker.

one more
first time I have sort of had it completely together. Finish still needs a TINY bit more work.
And per the earlier conversation, THOSE are the redwood leaves we were talking about.

Waffle: gorgeous
Stunning! I have a new appreciation for redwood. Just don't put anything on it!
And with the one without leaves, I'd make the new leaves out of re-milled glued up readily available redwood.

nope
It needs some kind of finish as, yes, it is fairly soft. What I am using 1) adds no color, minimal tone and 2) won't build up. Just a coat or 2.
Am pretty happy with the refinish. Allows the redwood to look like redwood.