Pardon the double post.

I've given it some thought: I think a mixture of the two so far suggested methods works best for what I want to do with Senko.

She splices herself with bloodlines... But she's looking to improve what she has instead of giving herself new stuff, so unlike Kabuto who gets a bunch of really weird stuff, Senko gets minor enhancements to her base state and to her sage transformations.

Senko splices herself with Lava style, she gets a handful of vaguely "lava" themed uses of sage transformation, affinities to fire and earth, and slightly better Chakra control. Same with other elements.

She splices herself with Uchiha DNA... Her vision gets slightly better and whatever other benefits she gets would really depend on the Uchiha in question.

She tries to give herself dead bone pulse, and very little actually happens becuase she can theoretically already create spikes and weapons from her body and make herself ultra durable.

She absorbs blood from an Uzumaki, she gets the power to form powerful chains out of her flesh and blood(as sage transformation version of Adamantine chains...) and the extended life span.

And so on and so forth.

Once she absorbs four or five, she hits a point where she tips over and her chakra control becomes good enough to actually learn real techniques and likewise gains partial access to the absorbed bloodlines: Ability to do nature transformation and the like. Basic techniques.

She'd gain full access to those bloodlines in Sage Mode, but she'd still have to learn to use them and I imagine that Sage Mode achievement is a Jonin level thing at bare minimum.

Theoretically, she could give herself every bloodline this way, but after she gives herself enough to control her chakra properly there are serious diminishing returns on investment.

I'm also imagining that each infusion of cells results in mandatory downtime. I've got the mental image of her spending a week in bed fighting off a bad fever after trying to give herself lava, scorch, or boil release.

Does that work?