Hi Matt. The Core package is good enough to get you going. Whether you exceed it's capabilities depends on where you were before you packed up.
If you were usually top-ten at National level, then it's going to frustrate you fairly quickly. If you were a good club driver then it will get you where you need to be and support your driving for quite a while.
I'd be inclined to get it and use it, because if you do feel it is holding you back then it would be ideal for Matt Jnr.
A 1S LiPo may work with a brushed ESC. If the ESC was designed for 6-cell racing then it won't work. You will need to run the car with a receiver pack or an RC Dynamics booster to get the 1S cell to work with a 6-cell speedo.
If it was designed for 4-cell racing then it might work and is well worth trying. Electrically there is no problem running BR motors/speedos with LiPo cells. When the cell gets low on voltage the whole car might stop. If it does, then it needs a receiver pack/booster fitted.
No, the current Mardave Porsche body is not legal for BRCA events. Note the legal shell is part number V113 and the current Porsche is part number V164. The full list of approved shells for Nationals is
here. HTH
