...

1) A JNLP file (that connects to all the correct resources etc.)
2) A server that will serve the JNLP file as the correct content-type.
3) As a bonus, add a web page that checks for JWS and
prompts download if not found.

I guess that is a question, though questions usually end in '?'.

See 'part 2' above.  The host needs to either ensure that
mime-type is set, or allows you the ability to set it for
yourself.

Ditto the question mark - they are handy for the reader..

Any (partly competent) host should be able to provide
that simple requirement, it is not as if they need to
run a 'servlet container' to get (basic) web-start working.

I have used LunarPages, and consider them to
be a bunch of useless incompetents on whom
I would not waste urine should they be on fire,
and currently user Prokmu*, who are fine..

But then, both those choices were specifically made
on the basis they provide a servlet container, which
is not needed for basic web-start.

* Reasonably priced plans - huge file-space and
bandwidth, excellent support.

Andrew T.