Japanese Verbs Are Like LEGO Blocks

Now, after four posts on Japanese verbs I've got an idea that Japanese verbs are like a blocks of LEGO.
And, looking at my previous posts, I see that the plain (dictionary) form is not a single LEGO block but rather a combination of two blocks: a vowel or few that form a "stem" and following vowel(s) that ends with U. This U ending vowel gets lost every time you conjugate a verb.

From now on I'm going to use a stem as a verb conjugation building block, rather than build everything the "dictionary" form. Look how easy it becomes:

Group 1: ~ U ending verbs (godan)

to speak（話す） hanasu はなす hanashimasu はなします hanasanai はなさない　hanashimasen はなしません
to write（書く） kaku かく kakimasu かきます kakanai かかない　kakimasen かきません
to listen （聞く） kiku きく kikimasu ききます kikanai きかない　kikimasen ききません
to wait（待つ） matsu まつ machimasu まちます matanai またない　machimasen まちません
to drink（飲む）momimasu のみます nomimashimasu のみまします nomimasanai のみまさない　nomimashimasen のみましません

Notice that sometimes romaji LEGO is no 100% match to kana LEGO - you can't make stems "kak" or "kik" in kana. And, "shimasu" definitely looks much better in kana :)
Also the stems I figured out do not match to common definitions of stems sometimes.
Common definition of "matsu" stem is double definition "mat -" "mach-", not "ma-" like I used above. Same for "hana-" and for other "su" ending verbs.

My guess is that this minor trouble with stem digging is caused by the fact that the stem is actually a kanji part of the verb, and that kanji-stem changes it's phonetics on reading. Since I did not mastered kanji yet (my deepest apologies come here), I may need to pay attention to the dictionary form to manage verbs with "su" endings that transforms to "shi" and "chi" for now.

Let's continue to exercise this bloody vivisection...

Group 2: ~ Iru and ~ Eru ending verbs (yodan)

to wear （着る） kiru きる kimasu きます kinai きない　kimasen きません
to see （見る） miru みる mimasu みます minai みない　mimasen みません
to get up （起きる） okiru おきる okimasu おきます okinai おきない　okimasen おきません
to get off （降りる） oriru おりる orimasu おります orinai おりない　orimasen おりません
to believe（信じる） shinjiru しんじる shinjimasu しんじます shinjinai しんじない　shinjimasen しんじません

Wow, some kanji stick to kana to form a stem, 起き for instance. And, as always yodan are a snap! Thanks to Yoda!

Group 3: Irregular Verbs くる (kuru) and ~する (~suru)

to come (来る) kiru きる kimasu きます konai こない　kimasen きません
to do (来る) suru する shimasu します shinai しない　shimasen しません
to study（勉強する）benkyou-suru べんきょうする benkyou-shimasu べんきょうします benkyou-shinai べんきょうしない　benkyou-shimasen べんきょうしません

Kiru was weird, "to wear" sounds exactly like "to come" in 3 cases of 4. Suru is weird also. So they are an irregulars for real.