Rumors are circulating that both Mercedes Benz and BMW are planning to develop mini roadsters to taken on other similar-sized roadsters such as the Mazda MX 5 / Miata. Mercedes’ hot little convertible is said to be based on the platform from the 2011/2012 Mercedes A Class and B Class, and is expected to a feature front wheel drive setup, instead of a typical rear wheel drive arrangement.

According to Auto, Motor und Sport, the mini roadster from Stuttgart which could hit the market sometime in 2012 is also expected to feature design cues based on the Mercedes SLA project, which is an 8 year-old concept. Power plant wise, there may be at least four engine options to choose from, with a diesel unit being one of them. The roadster should also carry a fabric convertible top, instead of a more fashionable foldable hard top to save space.

Over at Munich, the BMW Z2 mini roadster is said to be based on the current BMW Z4 platform, and may hit the market a little earlier in 2011. The Z2 should retain the rear wheel drive setup and feature a 150hp 4 cylinder engine, while there may also be a range topping 300hp variant with twin turbochargers.

BMW will most probably also offer an electric powered model of the Z2, but there is no news if Mercedes will offer a similar emissions free version of its mini roadster. Mean while, you can expect the BMW Z Vision Concept to be previewed sometime towards end of the year which will showcase potential design cues for the baby Z4.