I'm afraid you'll be designing a system that will never pay for itself. As a rough idea the cost in fuel will be between 2 - 4% of the weight of your gadget per hour. It will also rob the carrier of the weight of the device, weight which could be sold and valuable cargo space. Also, I'll also guess the braking action of a foam covered runway will be less than that of a dry or come to that a wet runway, thus increasing the length of runway required (and chance of over-run). Fire may be suppressed, but given the response times of fire crews at airports, that may also prove to be a waste of time.
As for the propulsion, the slides are powered by compressed gas and an aspirator, a sort of mass flow entrainment device that makes up for the lack of volume in the compressed gas. The slide canisters could not be used for any other purpose and would also be lacking in volume to pump any worthwhile volume of foam.
In an emergency, no aircraft pump could be relied upon - possibly the reason for emergency in the first place.
Lastly, runways are generally resistant enough to take the occasional belly landing and most aircraft appear to be scrap after a gear-up event. The loading on parts of the aircraft not designed to be in contact with the ground means extensive checks will make repairs uneconomic (eg. B747 in Cape Town).
As for hold dimensions and technical drawings - they might be difficult to get as they will be Boeing copyright. But your biggest challenge will be certification. It's tough enough fitting already approved components, let alone ones which are original.
As for an idea as to what could be designed -
1. A simple, cheap, lit, guidance system (search for Nose in Guidance Systems). The cheapest ones on the market are apparently now in excess of £20,000 each.
2. Combined tug, GPU, A/C and Jet start device.
3. Mirrors for aircraft stands so crews can monitor proceedings around the aircraft. If correctly designed, it could also do the job of No. 1 above.
4. An aircraft recovery device to enable crashed aircraft to be moved quickly.