Is your feature request related to a problem? Please describe.
If you want to add more realism to PHPVMS then of course you can set up a subfleet record for a single class A320 and a multi class version. Albeit you would need to create an Airframe Record on Simbrief for this purpose for every variant from the base A320 you choose and then set up all the data in Simbrief and copy the simbrief internal ID into your subfleet record. The problem with this is that if you share these Airframes or use an existing code then the data could change without you knowing and your subfleet information you once had is incorrect i.e. if somebody decided that a multi-class A320 had a maximum seat capacity of 140 economy and 20 business and then somebody else using that record changed the maximum capacity to 135 because they wanted 5 more business seats then the ofp would change.

Describe the solution you'd like
Depending on having as much data about a subfleet type and extending the data to be more inclusive of additional aircraft specifications at present MTOW and ZFW are there but not used , so we can use these types of figure in a special parameter in the SimBrief API call.
I have copied the notes below as follows -:
Note regarding Aircraft Data

Specific airframe data, such as aircraft weight limits and onboard equipment, can now be specified using the “acdata” parameter. This data must be passed as a JSON object, for example:

{"cat":"M","equip":"SDE3FGHIRWY","transponder":"S","pbn":"PBN/A1B1C1D1",
"extrarmk":"DAT/V RVR/250 RMK/EXAMPLE","maxpax":"146","oew":96.5,"mzfw":134.5,
"mtow":169.8,"mlw":142.2,"maxfuel":42.6,"hexcode":"123ABC","per":"D","paxwgt":230}
The following parameters can be specified: “cat” (aircraft weight category, i.e. L, M, H, or J), “equip” (the aircraft’s onboard equipment string), “transponder” (the transponder type), “pbn” (performance based navigation string, must start with “PBN/…”), “extrarmk” (additional info to be included in Section 18 of the ICAO FPL string), “maxpax” (the maximum passenger count), “oew” (the operating empty weight), “mzfw” (the max zero fuel weight), “mtow” (the max takeoff weight), “mlw” (the max landing weight), “maxfuel” (the max fuel capacity), “hexcode” (the ICAO Mode-S Code), “per” (the ICAO performance category), and “paxwgt” (the average passenger weight to use, in pounds). All weights except the paxwgt value must be in thousands of pounds, but can be specified with up to 3 decimal places (in order to set precise values). Also note that for the “cat”, “equip”, and “transponder” options to work, all 3 must be specified. If one of the 3 parameters is missing, all 3 will be ignored.

Please ensure that your JSON string is properly encoded to be passed in a URL, otherwise it may not work correctly.
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Now that would return full control to the Virtual Airline to control subfleet characteristics and also this data could be used for better OFP planning for the pilots rather than just use the A321 standard in Simbrief

Describe alternatives you've considered
Yes you can use the standard Simbrief OFP aircraft profiles and create your own and use the Internal Id. However I am sure somewhere this data can be used in tours and charters to price fares as you could set hire cost of the aircraft for a charter flight and then after costs etc you divide the total cost of the charter by the number of passengers for the subfleet and then you get a nice fare price.

Additional context
Add any other context or screenshots about the feature request here.