hi mate, welcome to the club.
i recognised your username from the MR2OC, i had a red rev 3 on white kei office wheels that started out NA and got turbo'd (amongst many other things), posted as stevie_mr2 and was regional rep for the northeast at one point. you might remember me, might not, i lost interest in the club and hadn't logged in in about a year when i bought my altezza lol.
only had mine for a month or 2 so i'm in a perfect position to answer your questions.... you might not like the answers though lol.
sat nav - you dont update it, transplant the whole system from an IS or forget it
CD player - famous for eating CDs, not seen someone get their cds out of one in all the threads i've browsed on this forum
remote - its japanese, so if you really want it you need to find a breaking altezza with one... and it'll still be no use to you, because its japanese
TV- you hit the nail on the head, it's designed to run off japanese bandwaves. i'm gonna take my screen out and retrofit another one in the enclosure, but again i haven't seen a working altezza screen here or anywhere else for tv. mine gets a lovely snowstorm though
other things: diff oil and gearbox oil.
5w30 fully synthetic if you can get it. stick anything else in and your vvti will take ten years to operate... yes i'm serious, it has a noticeable effect - mine did
air filters - mine had a TRD in when i bought it, can't speak for the worth of other filters really. no IS ones wont fit, they're a different shape - you need a 3sge altezza specific one, it should be rectangular
spark plugs - all iridium plugs do is prolong life. but they're easy to get hold of, so go for it