While I do understand some people could need a recording feature to use it creatively, I still think it would turn the whole program into a truly heavy and complicated plugin.
I sometimes do create custom patches myself with my own recorded samples and honestly I feel better and more flexible to record, edit, and manage samples in a dedicated environment (ie. audio editor) rather than doing that in an hosted plug-in.
I just consider the software sampler as a piece of software allowing me to manage and edit raw samples, sampling CDs, sample libraries, etc. other than play them back.
If you need recording on the fly, you can always record whatever you want into a track of your sequencer and then export/import that into the sampler. That’s faster than you think while you have your sequencer and Halion already opened.
Just an opinion 