Do you have any latitude/leeway on the svn repository arrangement? Can you rearrange it? If so, you might consider getting everyone to check in to the trunk once, cleanly, then make a private developer branch for each developer. Then "close off" (by convention) development on trunk.

If you can do that, then everyone develops in their own branch, so no more conflicts. Trunk is then used only to periodically merge the developer branches. Generally, this will be followed by tagging it and then probably pushing back to the developer branches. Up to you if you want a convention of periodic tags vs. tested and known stable tags, but that's just a naming convention.

Obviously, someone gets the unlucky job of SCM/Build Master to manage trunk and tagging. With some education, you may be able to push back on the developers to keep their own development copies in sync, or brute more force by just giving them a new copy of the latest tag. It's almost like git, the hard way (and no actual local copy of the repo...)