We use Graphhopper for our GIS sollution. The pressure to deal correctly with the complex turn restrictions is increasing so I would like to discuss two points:
Is currently worked on this? There is an open issue (#446) but I cannot figure out if this is on the roadmap.
We probably need to decide if we put ressources in switching to OSRM or improving Graphhopper (the solution we would prefer) if this feature is not on your roadmap. Would you be interested in us (java developers) working on this feature? Would you be willing to accompany the development and support it with your know-how?
Sure. Feel free to create a pull request. Also please see the issue as it might be that someone outside of the core team has implemented it already, but no pull request was created so far.
Not by default, but of course you can enable turn costs also for bikes. You have to make sure that the turn relation parser accepts bike turn restrictions though.