Circling back - if panning carriers uniquely is what you're after AND you already have multiple FM-X Parts - then you can "jumble them up" to have the two Parts representing two different pan positions then put different halves of both of the original Parts into one Part and the remaining halves of the the original 2 Parts into the 2nd Part. So instead of using Parts for different sounds - you take half of the carriers (the half you want panned on one side) and of one Part and combine them with carriers of the 2nd Part that want to be in the same pan location. This may mean getting creative with the algorithm to generate the equivalent. Since there's only one feedback - this may not work out so well if you want the feedback portion of two different Parts to combine into one Part. That won't work so well at least for "plug and play". But - ignoring feedback ...

Part 1
=====
[L] [L] [L] [R] [R] [off] [off] [off]

Part 2
=====

[M] [M]
[M]. [M]
[L]. [R] [off] [off]

... then combined you're going to want to reconfigure as

Part 1 (now the "left" panned part combining two above carriers that we want on the left side)

[M]
[M]
[L] [L] [L] [L]

Part 2 (reconfigured w/R carriers)

[M]
[M]
[R] [R] [R]

The bold content comes from the original Part 1.

Of course - Parts carry lots of things with them that cannot just be "combined"/"merged" if you're doing something like this. You'd have to live with the same insertion effects and same other parameters that are Part-common and possibly make compromises. However, under certain conditions - you may not need to "burn" as much as "swizzle".

I don't know if you're using more than one FM-X Part already or not. This may not help you out one bit for what you're doing now.

As such - this isn't a magic bullet. It's a limit-use resource balancing act. I'm not looking at exactly what you've got going there either as your typical user Performance with FM-X when this kind of thing comes up or knowledge of your sound design concept.

I do also see lots of places where it would be helpful to extend the functionality and agree that there are times like these where it would be nice to be able to do something more granular at the Part level to avoid burning resources. I've asked for similar things before. Given that it may be a while before any of these materialize - one needs to develop creative solutions with the functionality as it stands today.

Some extra afterthoughts.

Regards EQ
You can certainly brighten a Part/Performance with an EQ. The problem is they do not move or evolve with the note being played. They blanket affect everything.

FM-X Tutorials
There are some FM Articles/Tutorials on here written by Manny Fernandez. They are excellent. There is a "Beginner Guide" and an "Advanced Guide". They take some time to work through, but they are backed up (per lesson) with YouTube Videos (the audio is all that matters here).

If you decide to go through these, pay particular attention to how Manny uses Operator Amplitude Envelope Generators, and the very basic Pitch Envelope Generator on Modulators to generate Brightness in the Attack/Decay portion of the sounds. For example the first "Hard Blow" into a Trumpet often rises it Pitch and Brightness very briefly, this effect can be achieved by setting a Modulator's AEG and PEG to briefly "Hard Modulate" the Carrier (or subordinate Modulator).