What about using -ve as first person singular present tense ending? It is first person dual ending in Church Slavonic (-v'e) and in Slovenian (-va). It could be one way how to avoid the -ju/-m decision, but I guess you won't like it.

Can you show some examples?

Zdrav mozxju Oilensxpigel!

Li es Ojlensxpigelova tvoi zxena?
Ja dumajm zxe "Oilensxpigelvoi Idea" es naidobrju variant.

no doubt the slovio solution, if it had conjugation, would be -(i)wq
even though it's not Slavic sounds, but Arabic it's still a unique ending!

qpio skribal:
no doubt the slovio solution, if it had conjugation, would be -(i)wq
even though it's not Slavic sounds, but Arabic it's still a unique ending!
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Eulenspiegel II is dead, long live Eulenspiegel!

congratulation piqo, Eulenspiegel III, may Your reign be fruitfull for the everlasting project of Slovianski.

In eulenspiegel we trust!

If you didn't know, the -ova ending in those languages with femalised versions of surnames comes directly from the natural Slavic possessive ending -ov. In the past, there was Mr Ulens^zpigel with his wife (Ulens^zpigelova z^zena) or his daughter (Ulens^zpigelova doc^zera), while the latter forms were later shortened to Ulens^zpigelova. Feminists might not like it, but this is just how it is.

Which Slavic language would the "-voi" ending come from?

In Slovio, it would look like this:

ja razmnozxive
ja rodive
ja kormive
ja rastive
ja oplodive
ja upotrebive
ja vlozxive
ja dosagive
ja vbrizgive
ja raztiagave
ja snesive
ja smertive
ja pozxirave
ja viluskave