Figure subnumbering 1a

Figure subnumbering 1a

I'm wondering how to give subnumberings like "2a" and "2b" for separate floats. I know both the subfigure and subcaption packages do the subnumbering but they demand the subfigures be in a single figure environment.
For example, I'd be happy if I find an environment "subfigures" like this:
\begin{subfigures}
\begin{figure}
  A figure comes here.
  \caption{\label{first}Caption text.} %--> Fig.1a
\end{figure}
\begin{figure}
  Another figure.
  \caption{\label{second}Caption text.} %--> Fig.1b
\end{figure}
\end{subfigures}
It's basically the same as AMS LaTex's subequations environment.
The reason why I want to do this is that I can't decide how I should group my figures until much later in my writing process. If I had an environment like the above, all I would have to do is to cut&paste figure environments or delete or add subfigures environments in order to reorganize my figures.
Since what I want is very similar to the subequations environment, I guess I can make my own subfigures environment after enough hacking, but I'm not much versed in TeX coding and am wondering if there is already a solution available.
Thanks for your help.
Ryo