Hi Chad,
There was a version for 7.5. If the customer does not already own the licence for eConnect 7.5 then I'm not sure you could even purchase it now from Microsoft. We did a lot of heavy eConnect stuff in 7.5 (cut our teeth on it!!) - and while its was a little bit buggy at times - it was fit for purpose.
The best bet would be to upgrade GP to a supported version and use the compatible version of eConnect.
Re: writing directly to the tables...We have cleaned up too many custom integrations over the years to be able to recommend it under anything but the most dire circumstances. You're preference for eConnect is spot on. Its usually non GP technical people that say - 'sure, its just writing to SQL tables. Lets study what GP does...and replicate that'. Problem is it goes into production and they end up running scripts and checklinks to try and fix data. The problems usually don't appear until you try and upgrade and GP utilities starts complaining about missing data etc. Stick to the Microsoft supported methodology of using eConnect (when consultants see stored procedures freely available to them, they come up with all sorts of wonderful (and unsupported) ways to use them).
Best regards,
Ian.