The L-twoo Fold-B is the only derailleur able to keep the chain tensionned when folding the rear triangle.

The type of chain tensionning with an extension arm added to the derailleur cage of the Takachia was used on the Birdy 1 and Birdy 2 (mounted at factory by both Riese & Müller and Pacific Cycles and also several different design from several third party components manufacturers like for instance Ridea) and has never been 100% reliable = without derailling sometimes when unfolding the bike.

It would be better to keep the L-twoo Fold-B derailleur.