Hello. This is my attempt to add this-> https://github.com/ftvkyo2011/xkb-custom layout.
It's useful because you are able to remember only one position for all punctuation keys
and should not worry with "Where is the colon? What language am I typing in?"
It's tested on me for ~1 year at this moment.

Here are the files ("diffs" :D ):
They were tested on my computer (Arch Linux) with the following commands:

./autogen.sh
make
sudo make install
sudo mv /usr/local/share/X11/xkb /usr/share/X11/xkb
setxkbmap -layout "us,ru(unipunct)" -option "grp:caps_toggle,lv3:ralt_switch,grp_led:scroll"


//// FROM 579 LINE OF rules/base.extras.xml.in

        <variant>
          <configItem>
            <name>unipunct</name>
            <_description>Russian (with US punctuation and some 3rd-layer keys)</_description>
          </configItem>
        </variant>


//// THE VERY BEGINNING OF symbols/ru:

// Keyboard layouts for Russia.
// AEN <aen@logic.ru>
// 2001/12/23 by Leon Kanter <leon@blackcatlinux.com>
// 2005/12/09 Valery Inozemtsev <shrek@altlinux.ru>
// 2018/07/15 @a13 (a.k.a. @dbvvmpg) and Stepanenko Andrey <ftvkyo2011@yandex.ru>
...


//// THE VERY END OF symbols/ru:

partial alphanumeric_keys
xkb_symbols "unipunct" {

// Раскладка представляет собой обычную русскую раскладку, в которой
// некоторые редко используемые буквы убрали на третий уровень,
// и поставили все пунктуационные знаки на то же место, где они
// стоят на US раскладке.

// ru(unipunct):
// `~ 1! 2@ 3# 4$ 5% 6^ 7& 8* 9( 0) -_ =+
// хХ бБ уУюЮ кК еЕэЭ нН гГ шШщЩ жЖ зЗ [{ ]} \|
// фФ ыЫ вВ аА пП рР оОёЁ лЛ дД ;: '"
// яЯ чЧцЦ сС мМ иИйЙ тТ ьЬъЪ ,< .> /?

 include "us(basic)"
 name[Group1]= "Russian (with US punctuation)";

 key <LatQ> { [ Cyrillic_ha,   Cyrillic_HA ] };
 key <LatW> { [ Cyrillic_be,   Cyrillic_BE ] };
 key <LatE> { [ Cyrillic_u,    Cyrillic_U, Cyrillic_yu, Cyrillic_YU ] };
 key <LatR> { [ Cyrillic_ka,   Cyrillic_KA ] };
 key <LatT> { [ Cyrillic_ie,   Cyrillic_IE, Cyrillic_e, Cyrillic_E ] };
 key <LatY> { [ Cyrillic_en,   Cyrillic_EN ] };
 key <LatU> { [ Cyrillic_ghe,  Cyrillic_GHE ] };
 key <LatI> { [ Cyrillic_sha,  Cyrillic_SHA, Cyrillic_shcha, Cyrillic_SHCHA ] };
 key <LatO> { [ Cyrillic_zhe,  Cyrillic_ZHE ] };
 key <LatP> { [ Cyrillic_ze,   Cyrillic_ZE ] };

 key <LatA> { [ Cyrillic_ef,   Cyrillic_EF ] };
 key <LatS> { [ Cyrillic_yeru, Cyrillic_YERU ] };
 key <LatD> { [ Cyrillic_ve,   Cyrillic_VE ] };
 key <LatF> { [ Cyrillic_a,    Cyrillic_A ] };
 key <LatG> { [ Cyrillic_pe,   Cyrillic_PE ] };
 key <LatH> { [ Cyrillic_er,   Cyrillic_ER ] };
 key <LatJ> { [ Cyrillic_o,    Cyrillic_O, Cyrillic_io, Cyrillic_IO ] };
 key <LatK> { [ Cyrillic_el,   Cyrillic_EL ] };
 key <LatL> { [ Cyrillic_de,   Cyrillic_DE ] };

 key <LatZ> { [ Cyrillic_ya,   Cyrillic_YA ] };
 key <LatX> { [ Cyrillic_che,  Cyrillic_CHE, Cyrillic_tse, Cyrillic_TSE ] };
 key <LatC> { [ Cyrillic_es,   Cyrillic_ES ] };
 key <LatV> { [ Cyrillic_em,   Cyrillic_EM ] };
 key <LatB> { [ Cyrillic_i,    Cyrillic_I, Cyrillic_shorti, Cyrillic_SHORTI ] };
 key <LatN> { [ Cyrillic_te,   Cyrillic_TE ] };
 key <LatM> { [ Cyrillic_softsign, Cyrillic_SOFTSIGN, Cyrillic_hardsign, Cyrillic
_HARDSIGN ] };
};