Seems like a lot of work, just to run one broken client. Have you
tried contacting the developer of the client to see if they can simply
fix it to use OAuth?
The SuperTweet.net service already serves a niche, or IOW a small
percentage of Twitter users, but it's a big enough niche to justify
the service/efforts. We support this niche because we believe it is a
legitimate problem and serves a community - i.e. for the good that
SuperTweet.net does.
The niche of people wanting to use closed-source apps that could
certainly simply be fixed to support OAuth but for which the developer
will not either (a) fix it, or (b) open-source the app so someone else
can fix it, is a niche I don't care to serve for reasons of size and
significance - it doesn't have the same benefits to a wider good. It
instead helps enforce bad behavior, supporting those that won't fix
their apps nor release the source code to them so someone else can fix
them.
It would be best to start with a different code base than SuperTweet
for the solution you're looking for. Sorry.