As someone who quite enjoyed Titanfall, I've enjoyed playing Necramechs (levelling them however...) and I'd certainly like to see more places where we have the option of using them, because as much as I like my big stompy mech, I know that there are others who don't, so it isn't fair on them to be forced into using something that they don't want to use. The name of the game is Warframe after all.
That said, I'd also like to see Corpus/Grineer* takes on Necramechs, maybe as an elite enemy that appears on The Plain's/Orb Vallis that drops Necramech mods/weapon parts (maybe as part of a special bounty mission?). Again, like the enemy Necramech's we encounter in the Isolation Vaults, we should have the option of being able to defeat them with either our Warframes & regular weapons, or fighting them with our own Necramechs.
* I'd imagine that a Grineer Necramech would probably be something like a W40k Killa Kan, except with with Grineer aesthetics, while the Corpus would probably be an oversized Moa/Ambulas except with side mounted weapons instead of the usual head mounted one.