Perhaps your organization believes this: "Tcl seems to be an interesting language, but if we use it to solve a problem, then we'll forever be at risk for losing all our Tcl expertise with no effective way to replace it." Your organization would be correct, of course, in its awareness of the strategic nature of its information technology (IT) assets.
Tcl's part of the solution, though, not part of the problem.
[Explain contracting possibilities, acknowledge hiring mis-practices, distinguish Tcl "learnability" from C++, ...]
RS Tcl skills are less frequently in the market than, say, Java, but