Something simplistic: maybe, something custom... probably not. There's nearly always more value in using something that other people use too due to the positive network externalities. Granted, they may be weaker in cases like this where there is not a great deal of code sharing, but one-off languages tend to end up being a burden.

Which is why they seem to have ended up with Lua, which is probably the best fit for that problem domain. Cut down versions of Tcl probably would have been ok, and have been successfully used for things like embedded systems, but probably are more work than Lua, which is 'cut down' by default.