To be fair Lucas changed his originial intentions for New Hope when he realised it was going to be the first film, he tacked the Death Star on(originally only meant to be in the finale Jedis) in order to give it some punch, there's similar ending with the Control Ship in Episode I, you'd still have that.
TF droids would probably just become men in battle armous, maybe as robots maybe not, a 'Sith' would feature more promenently rather than a few brief bits and a big fight. Perhaps most horrible such a POD would doom Darth Vader almost completely as we see him. Originally Vader and the Stormtroopers were intended to 'fly' over to the rebel ship in Ep.4 with space suits, his iconic mask simply being the graphic artist's idea for the suit. Lucas liked it, scene got cut, kept the cool mask. Really bar the flow of the plot little will stay the same in the name of entertainment, its space opera not a LotR adaption.
Anakin will probably be older, allowing a more immideate love thing with Amadala, make the head of the Guard a more tough action rogue figure and bam still got a traditional band of heroes element. Due to effects the swamp Gungans become something similar like... men in bear costumes? Bam, wookies become the noble savages of Ep.1
Really the whole saga reuses myth tropes and movie set pieces all over, the first 3 films would be nothing like our prequals in order to make fun films, while the second set might end more cubersome things more foused on the grand story than entertainment.
Guiness still gets cast for star power, maybe as Obi-Wan, maybe as Qui-Gon, either way just throw in another Jedi Apprentice who is Anakin's rival, have his character become the mystic mentor for the second trilogy.