That's very much along the lines I'd be thinking. That's the lowest cost option, but I'm really attached to having VO in games, even if it is just a couple 1000 words. Get a lot of enjoyment out of writing the intros, and getting back good VO work that brings it to life. Think it helps quite a lot establishing atmosphere, though as you observed, maybe it takes something away too.
Regarding illustrations, if the illustration is anyway up close, and characters are realistically proportioned, you just wouldn't get away with replacing the head in the vast majority of situations. Olga would probably refuse
The entire character would need to be redrawn in every scene, so if was considering this route, would be inclined to include protagonist less in illustrations, or more distantly, or from a perspective where less detail is required, or stylise the art in such a way as to reduce the amount of work required. Also, each artwork commissioned costs funding and one of the biggest (if not the biggest) factors in final quality when working with limited resources, is being incredibly careful in how you allocate them.
There are going to be quite a few smaller things to consider too, many of which may not be obvious until they become a problem.
I have a basic system like that in place, which modifies the text based on gender of speaker, but it's currently only set up for third person. I will give this serious thought for next game, assuming it's same genre, quite a lot of the basic systems will be in place, so will be able to pursue other features.
I think if I had extra capacity this time around, to make the best game possible, it would be best to work on features (like improving the crafting system, or making enemies present more varied tactical challenges) or build out the content.