Deinterlacing is going to cost you resolution. It seems many people deinterlace simply because they end up with field order problems and this seems to be the lazy way to fix them. SD is interlaced.
That said, many like the so called film look of progressive so they deinterlace. If you want the look then search the forum here for many recommendations for good deinterlace plugins. Don’t use the FCP one.
Having both HDV and AIC in the same timeline is not a problem. I would recommend changing your render setting to ProRes so that after grading & filters, your final render is in ProRes. Make sure your drives can handle the extra bandwidth by doing a test or checking with a disk speed program. Both Blackmagic & Kona have these testers for free.