Regarding 'string memory' - I've never found it to be a problem with steel strings, but nylon strings do it very noticeably.

As to whether to use open tunings or not - so called 'standard' tuning is really just one of many tunings used over the centuries, and there is no reason to suppose that it is any better than any other tuning. It simply standardises things for written notation, but it certainly ain't logical!

I believe in getting the sound you want, not the sound you are given. If that means retuning one or more strings, then do it! If you're happy with 'standard tuning' (I use it a lot, anyway), stick with it.

It's all down to personal preference...