Storing my Lambda Functions on GitHub Will it be practically possible to build some pipeline; 


starting from rapid AWS Lambda function development using blueprints, 
to store them later on a new GitHub repo, 
that is linked to some CICD such as Travis, 
that will in turn deploy successful builds back in AWS Lambda?
Your idea will work. The organization I work for maintains some open source examples how to do deploy to AWS using a pipeline. In comparison we use GitLab for the purpose. Instead of Travis we use GitLab Runner. You configure it using the file .gitlab-ci.yml which runs the tests and deploy the AWS Lambda to dev, test and production environment every time a commit is done.  You store your secret account variables in the CI/CD settings of the repository.

There are the usual drawbacks of AWS Lambda such as difficult or impossible to test and run locally and waiting for deployments takes time, but your deployment process will be good practice.