Automating Appending Assets objects with CustomFields from Issues

[Faith Ntundi]

I'm looking to automate our process that grabs fields from request forms and stores them in Assets. I'm using data center, so API calls (without using Groovy scripts) are not available (at least to my knowledge). Since I'm trying to future-proof the process without requiring plugin procurements (scriptRunner), what is a possible route to achieve the end goal here?
Is there an Assets API that I'm ignorant to? Are there Jira-native processes that I can use? Right now, I'm running a groovy script that creates a json file that is then imported into assets on a schedule. I'd like to have a JSM-native trigger that either triggers AAP to run the job of creating the output file that is imported into JSM directly, a JSM-native process that pushes the field-designated objects to the corresponding field in asset, and API that allows me to post objects to assets, or any permutation of the above. The goal is to ensure that neither paid tools nor access to the filesystem are required. Thoughts?