I actually did think of this connection when I saw him as Denethor in LOTR. 

For starters: his whole hair and makeup was perfect in LOTR, and the acting, too!

He even sets himself on fire like Magnus!

BUT I imagine Magnus as being scarily skinny, more spindly. He almost seems like a spider:

“…Rather
he leaned to rest, it seemed, upon the thick stone frame of the window,
one knee bent a little towards it, the other long spindly leg sprawled
out to the other side…

his thin, gangly limbs found animation ail at once.” – TVL

Look at John Noble outside of his LOTR makeup tho:

^This looks like the ID card pic for Raglan James to me ;D 

A man who, yes, has some solid weight on him because he enjoys fancy food, and not extra physical exertion, he’s older but still got a lot of life in him yet, and a kind of scheming default expression.