After talking with @cfr above, I realized that finding an alternative to bibLaTeX would likely be more of a headache than figuring out bibLaTeX itself.
Turns out, many of my woes were the result of my being completely ignorant with respect to the package. After some exploration and some tinkering, I came up with a MWE that does what I want:
\documentclass{article}
\usepackage[backend=bibtex,style=alphabetic, citestyle=alphabetic]{biblatex}
\renewcommand*{\multicitedelim}{\addsemicolon\space}
\usepackage{stoversymb}
\addbibresource{dissertation.bib}
\begin{document}
Some words \cite{Fenley1}.
Some more words \cites()()[pg~1]{Fenley1}{Calegari1}[par~123, thm.~4.1.2.7(a)]{C&D}
\printbibliography
\end{document}
The output:

I'm still not 100% sure that this solution will work with my overall project. Long story short: I'm writing a dissertation using a University-built (and -enforced) style file that is, at best, poorly written and clumsy (to the point that it takes away a lot of foundational functionality of packages like subcaption and subfigure, etc.). Even so, having this knowledge will make my attempts more streamlined and focused.
Thanks again for taking the time to put up with my poorly-presented question; I truly do appreciate your insight!
\cite[arg]{key}produces. Plus, the behaviour you describe may be somewhat similar to\citesbut it is certainly not 'identical' and, since you emphasise that mere similarity is insufficient, this seems problematic. Especially given that\citeswill not necessarily produce the results you state as desiderata if using Biblatex. So it can't hard code that and be 'identical' as a macro. Besides, why not use Biblatex? – cfr Jan 04 '16 at 02:21bibLaTeX, etc. :) – cstover Jan 04 '16 at 03:38