Open-source LMS setup with several customized elements

We are looking to launch an LMS to offer online courses to adult learners, via live video discussion sessions (with a self-paced learning option included). All relevant costs (including hosting, storage, backups, intermittent post-setup support etc.) need to be accounted for, please. Video content will comprise approximately 8 x 1.5GB videos per course, for ~30 courses. The LMS should be able to auto-allocate learner roles upon course completion (e.g., auto-upgrade a learner to a group leader/mentor role, upon completion of a certain course), keep track of learners' attendance of live video sessions from within the LMS itself (no third party tools), offer learners the option of selecting their language of choice in which to view different pages of the LMS, have e-commerce functionality to sell courses, and require relatively little admin interaction after initial setup. Preferably, the solution should be able to accommodate unlimited learner numbers.