I am starting (have started actually) a sizable project where I am building an Adeptus Mechanicum force which will range from the Skitarii, imperial knights, and a few super heavy vehicles and walkers. My plan is to make the weapons magnetized and swappable so that I can play them in 30K and use them as a counts as Imperial Guard + Space Marine force in
40K.
I do however need some advice;
My first question is are what are the "famous" skitarii armies, their history, and color schemes. The only ones I can seem to find are the red and copper color scheme which I believe is the one garrisoned on Mars. I don't care if they are loyalist or heretical I am more interested in the options.
Connected with the previous question are there any particularly interesting campaigns or battles which could inspire the basing? I prefer the bases to tell a story however I am currently stumped on the story for this force.
Of the forgeworld Adeptus Mechanicum model line which of the models is closest to being the size of a centurion? The ones that look close are the Castellax and Myrmidon however it is difficult for me to tell without the models. Does anyone have these models to compare? I believe that the Myrmidon are close to centurion size and the Castellax is dreadnaught size.
Can anyone figure out what a Thanatar Siege-Automata would work for as a counts-as in
40K. As far as I can tell it is closest to a dreadknight.
Is there any good counts-as in
40K for a Thallax cohort? I need an excuse to include them.
My current models I have and am going to use for my counts as are;
*Toughest Girls of the Galaxy for my skitarii; Hyspasists, Sagitarii, Balisteria crew, Cataphractii crew, Praetorian Storm Trooper level, and more human like Tribunes.
*
FW artillery is being used for the Balisteria; so thudd guns, earthshaker and medusa heavy artillery carriages, sabre defense platforms, and tarantula sentry guns. However they no longer sell manticore platforms. Does anyone know whether I can find some of these or are their alternative models that work well? The weapon would be workable by making the chimera mounted version removable but what is a good mount for this?
*
FW and
GW vehicles will be used for Cataphractii however does it make sense for them to have the eagle or will these symbols need to be removed and replaced with AdMech symbols?
*I am currently planning 2
GW imperial knights, 1 Dreamforge leviathan crusader for use as an imperial knight, 1 lancer, 1 castigator, 1 acheron, and 1 magaera for my imperial knights. Any other suggestions?
*I already have a very nicely painted (blue and steel color scheme) mars pattern warhound titan. So I probably wont get another or repaint. However if there is a reason I definitely should (perhaps another of the patterns is iconic) please convince me to go bankrupt...I mean make this investment

.
*I am also planning to avoid getting a reaver as the pts are so high I never get to play it. However if there is a good excuse then I would have to reconsider.
*I am planning to use Dreamforge Eisenkern Stormtroopers with bolters to act as Praetorians that have been modified to the level of
SM scouts (which they will be used as counts-as). However, I cannot seem to find anything that would make good AdMech that are at the level of Astartes in power armour and terminator armour. I also already have a
DA and
GK army so I am pretty sick of the power armour and terminator models from
GW 
. Somehow though I am not sick of the vehicles?
Thank you very much for reading this and thanks for your consideration. Sorry for asking so many questions in a single
OP.

Bad forum etiquette but I wanted to keep this together so please excuse me.