Is Workflow Manager 1.0 Viable?

Question

The company I've been working on will develop a new project and in this project, Windows Workflow Foundation 4.5 (we can't change it) will be used for process flow system which will be consumed by a web UI. Our main use case is order payment which has multiple steps in UI and in every state transition, UI will notify workflow instance that if provided values are valid. If it is, it will persisted and so on. (like http://examples.donnywals.com/angular-splitform/ ) It is designed as workflows will be hosted on IIS and every operation can be done about workflow(upload, delete, managing instances) should be accesible by a REST API. Also, workflow xaml files should be stored in database. Versioning, tracking and tracing and this kind of base operations should be supported too. While searching about how to achieve this goals easily, I encountered Workflow Manager 1.0. I would like to use WF 1.0 but;

1. It lacks of documentation. For example, I don't know how to consume it's pre build REST API without WorkflowManagerClient and no documentation has provided. Where can I find good documentation about it?
2. Last update in WM 1.0 was provided in 2014 and it looks like no one is paying attention about it. Where can I find a roadmap?
3. It seems like no one is using Workflow Manager 1.0 without Sharepoint 2013. Has anyone been using it without SP 2013 and did you satisfied with the result?
4. I need to update previous versions of workflows instances to the latest if possible but I couldn't find a solution about this in WM 1.0. Only possible choise is terminating previous version's instances or previous version's instances is allowed to work in previous version of that workflow, not the latest. Hasn't it provided or only it's not documented?
5. Activities for WM 1.0(such as HttpSend, GetConfigurationValue etc.) which was accessible from Workflow Designer in Visual Studio 2012 is not supported in VS 2013 and VS 2015. We use VS 2015 and I don't think that we could use VS 2012, isn't there a way to use that WM 1.0 specific activities?
6. If I shouldn't be using WM 1.0, it seems like I can't use WorkflowServiceHost either because of AppFabric servers will not be supported after 2016. Is my only option is WorkflowApplication?

Every piece of information is welcomed, thank you.

Answer 1

we are using WFM without SP for a product the we are developing and deploying within Azure. What I can say is that you have to work a lot to target your needs with WFM, we are working on it from more than 2 years and still today we are facing problems to get results out from a wf! by the way I try to answer to your questions:

1. There is no documentation about consuming Rest Api without WFM Client; times ago I directly asked to WFM team without an answer...so we use the client...
2. There was an update this year ;) Cumulative Update 3
3. Yes, me!
4. It is possible to let previous version to run till their end. Next "start" request (both whit .Start or .PublishNotification methods) will start the new version
5. No way to use with version higher of VS2012...you need (like us) to build your own editor. There are a lot of examples like this
6. The reason why I choose WFM is that I didn't want to use WorkflowApplication and do everything by myself...that is (I think) the only option you have (of course WFM has also a lot of advantage other than "simple" persistence)

Hope to be helpful.