I'm not an expert on this, but I understand there are (were) a lot of bolt-on suspension/chassis goodies for our cars for the weekend track warrior type. Mostly rare now and hard to find even in Japan. There are a few guys on a US based forum that track their SP20's (known as the Mazda P5 in the states). I'd join the mazda247.com forum and read, read, read the Protege5 section before committing to buying anything.
There's a lot of guys on that forum that could help with your track day SP20 enquiries. A few guys have built exactly what you intend to do.
See this thread for one option on suspension goodness!
http://www.astinagt.com/forums/showthread.php?t=19028