(Prolog + LISP + Erlang) with integration issues versus C++

[Dev Functional]

Hello

Given the insistence of the members of the team to use the
best language for specific purpose, we have code that is
written in
 1. Prolog (enumerating device drivers, goal seek)
 2. LISP   (classical AI stuff, inference)
 3. Erlang (server, communication and distributedness)

The products we have used are
 1. gprolog
 2. clisp
 3. Erlang/OTP

The independent modules have been developed successfully,
however we are unable to surmount the language boundaries
and connect Erlang to Prolog, Erlang to CLisp and CLisp to Prolog.

The team has quickly built the components (less than 3 months)
and proven the idea.

The management is worried about our choice of three languages
and has strongly suggested a relook at this strategy.

The External Consultant (Subject Matter Expert) has suggested that -
0. since the individual components are implemented,
   the idea is partially proven
1. the language barriers will cause problems in integration
   and performance
2. the long-term success and reach of the product will be
   based on complete implementation in C++.
3. The Visualizer will be implemented in OpenGL and C++ based modules
   will be quite easy to integrate.
4. C++ performance will be good if a ANN component is added later
   due to customer request.
5. Multi-language maintenance costs will be high

The team is disappointed, since the effort in learning the languages
will be wasted. The 6 developers are from C/Java background.

Greatly appreciate if the more experience members of this group
share their experiences and put forward the suggestions.

I need to present a case for the proposed solution, on the coming
Monday.

Thanks in advance.

thanks
Dev.