Daisy chaining XSLT and also how can I check whether t

Hi,
Currently, I am currently working with a product that outputs syslog output
that is formatted as XML, and the product also supports configuring an XSLT
that will process the raw syslog XML from the product, before sending the
transformed output to the syslog server target.
The product comes with a number of "out-of-the-box" (OOTB) XSLTs to support
different brands of SIEMs, like ArcSight, Splunk, etc.
The version of the XSLT appears to be "1.0".
We want to modify several of those OOTB XSLTs, but they are fairly large and
our modification would only alter one of the elements in the OOTB syslog
messages, so I wanted to implement an XSLT that just transforms that one
element, and then somehow causes the modified XML from my XSLT to be processed
by one of the OOTB XSLTs.

So, functionally, what I am looking to do is as follows:
Original flow:B  Product outputs syslog XML ==> <an OOTB XSLT> ==> syslog
server/syslogd
Modified flow: Product outputs syslog XML ==> <my XSLT> ==> <an OOTB XSLT> ==>
syslog server/syslogd


BUT, what I mean by the "<my XSLT> ==> <an OOTB XSLT>" part of the flow, is
NOT that the output of my XSLT is "sent" to the OOTB XSLT, but rather, somehow
MY XSLT would cause the OOTB XSLT to be processed.
[Apologies for the somewhat confusing verbiage :( !]

So, I was doing some searching and found these:
https://stackoverflow.com/questions/54814182/performing-chain-of-transformati
ons-in-xslt
and:

https://stackoverflow.com/questions/4571956/is-daisy-chaining-xslt-an-accepte
d-practice
>From those threads above, it sounds like what I thinking of doing is
POSSIBLE, but one of the requirements is the availability of an extension:
ext:node-set
So I wanted to find out:
a) How can I check that the XSLT processor supports that extension?B  Is there
like a small XSLT that I can test that would tell me whether or not the XSLT
processor that is running the XSLT supports that ext:node-set extension?B B 
FYI, when I am doing development of my XSLT, I am testing my XSLT initially
using xsltproc on a CENTOS machine, then, once my XSLT works, I then copy my
XSLT over to the product, and configure the product to use my XSLT, and so far
that much is working...

b) Also, I am wondering if anyone here has tried something like what I am
describing, the "daisy-chaining" of XSLTs?B  If so, are there any other
"gotchas"?

Thanks,Jim