Not sure if this was pointed out b4, but IMHO the SAF should have considered using the Russian BMP3 with a 125mm gun as a replacement light tank for the SM-1. Heck, even in it's IFV version, the 100mm cannon combined with 30mm automatic cannon would have offered much more firepower than the SM1's 75mm vintage cannon. It is also amphibious & at less than 19 tons(loaded), I think it might be possible to transport it via C130. Its internal might be pretty packed, as are most Russian armored vehicles, but then again, so is the Bionix II. If Russian reliability is an concern, STK could perhaps assemble the machines locally under license.
If a heavier armored "light" tank is required, the German TAM should fit the bill, provided that it's upgraded with better Fire control & sights. At 30.5ton, it's just slightly heavier than the Primus SSPH.