Right now we have some linqpad scripts that use 1.7.1 of NEST Elasticsearch and some using 2.4.5. But we can not share those/use them on the same machine since there is only one 'NEST' directory under Linqpad\Nuget, right?

Not sure how this would be handled since you want to upgrade etc, but maybe the diretory should contain the version number in it? Then you could in theory have 2 versions downloaded.