The whole point of version control is to prevent developers from overwriting other developers' source code. Subversion is a complete joke and handling branching and merging is a total nightmare. Simple solution: convert over to an intuitive SCM like git. Once you learn it, all the other solutions become stupid and irrelevant. Ask Linus if you don't believe me. ;)

"God gave us two ears and one mouth to remind us we should listen twice as much as we talk." - Author unknown