It seems like Kajishima himself doesn't know what he's writing anymore. OVA 1 and 2 emphasized the fact that Ryoko is madly in love with Tenchi and will do absolutely anything for him. OVA 3 showed this once again when Ryoko, despite knowing she was completely outmatched went to Tenchi's aid without batting an eyelid as she has done all along. The OVA series to me was written in a way to make Ryoko stand out and then he goes ahead and introduces Noike (Which I completely understand) to freshen things up and in the process completely pushes Ryoko to the side and now he's only left with 2 choices to end it.
Tenchi marries Noike because it's already been shown that no-one would dare go against Seto or he marries everyone including Sasami. Either way as a Ryoko fan the ending is going to be bittersweet because he's not going to actually choose Ryoko, he's gonna get the harem ending by default and for Ryoko it's either share him or lose him and we all know she would rather share him with the rest than lose him and I think that's a major copout on Kajishima's part.
You can't help but feel sorry for Ryoko really. She was used by Kagoto as basically a destroyer of civilizations and then she was locked away for 700 years. During which time the only thing she ever wished for was to be with Tenchi who has basically given her a new life. Then when she does finally get free, Tenchi gets surrounded by women who have fallen in love with him and now she's probably going to have to live with the fact that Tenchi's gonna be banging at the very minimum 3 other women besides her. Poor woman.