I open this topic for updates about the project.
The initial idea discussed between me, @Rik8119 and @fedde was to create a Multivendor Marketplace using an ecommerce platform (the one chosed by Fredrik Bodin was Opencart), in which goods and services' payment will be possible using two currencies both, a fiat currency and solidar. This will be possible implementing a modified split payment plugin. Ordinary split payment plugins give a way to pay with cash and cards both and was used first on offline POS. The modified split payment plugin will give a way to pay some partly in a fiat currency (euro, dollar, etc) and partly in solidar. In that way we think we could spread the adoption of solidar, because lots of phisical goods have a fiat currency production/distribution chain behind, so is needed to give vendors partly fiat currencies. When chains will be closed with solidar, the percentuage of solidar will increase.