One of the things that might initially baffle a CAD Manager or power user when investigating switching from AutoCAD to BricsCAD is how to set up the startup routines. Head over to CAD Panacea for R.K. McSwain’s concise, handy description of how to do it.
Due to BricsCAD’s high level of compatibility, you can maintain a common folder or set of folders containing LISP and other custom files for both applications. That way, you don’t need to do double maintenance during the transition period. I’ve done this successfully in a highly complex custom environment. Some code and other adjustments were required in places, but all but a handful of my hundreds of AutoCAD LISP files worked as-is in BricsCAD with zero effort.
Having added your AutoCAD custom folder(s) to BricsCAD’s search path, I suggest you make a common startup LISP file (e.g. rename your old acaddoc.lsp to something like CADStartupDoc.lsp) and have tiny stub startup LISP files for each application (acaddoc.lsp and on_doc_load.lsp) that each loads the common startup file.
You can add error checking and messaging if you like, but if you have control of your environment you probably won’t even need that. If you find you do need any application-specific code, you can just add it or load it from the acaddoc.lsp or on_doc_load.lsp stubs as appropriate.