Exactly this is the problem if there are three e's and one is è then in my opinion i should use some other letter for half sound (polglasnik) becouse i want my wrriting transparent and obvious. So there wouldn't be mistake between variant of e and schwa (polglasnik).
Heh, so the whole thing will be very profesional, ha?
I really don't see this problem… ??? Afterall in Slovene language, the "schwa" is only one of the e variants, isn't it? If I'd be you and do such a thing I wouldn't use a new letter but an already existing one. But since you would like to see where those schwa-s are (where otherwise wouldn't be any) – if I get that correctly – I would simply underline it. Any special crap you'll come up with will make only confusion. Izumlat toplo vodo ni nikol blo koristn. Naj bo enostavno, osnovno in s tem boš dosegu večjo preglednost in razumljivost.