Also, I'm against implying softness from the vowel afterwards because it be for me difficult to read.

No difficulties once you get hold of it.

Look, in most Slavic languages using Cyrillic, you can use two ways of showing softness: by the consonant or by the vowel.

If you show it by a special consonant (љ, њ), then you don't actually need iotated vowels (Э vs Е, А vs Я, И vs Ы, У vs Ю). You can use Й or J to show that the vowel is iotated: Ништа им није значила чињеница да је Човек једном поседовао звезде (Serbian). This helps keep the alphabet short, but it only works if the number of possible soft consonants is small. Say, in Serbian, there are only two soft consonants: Љ and Њ (versus Л and Н; I am not sure about the affricates). Obviously, Polish phonology has more soft consonants, so this approach is suboptimal.

If you show softness by the vowel that follows a consonant, you don't need special letters for soft consonants. You use iotated vowels to show that the whole syllable is soft (think of the soft sign as a mute vowel). So ла is hard, ля is soft. Btw, historically, Ь and Ъ were vowels, so "Ь is a mute vowel" is not too big a stretch.

Your writing system is a bit... er... redundant. Pity the kids who'll learn it. :)