[Revenant] is hands down the best Index point mule in Warframe. Mesmer Skin ([Revenant]'s 2) is immortality, and frankly better immortality than other frames' immortality. It's totally unaffected by Index point debuffs (unlike frames that rely on armor/health/shields to survive), it needs very little energy to sustain, it's totally immune to status effects, and it stuns enemies. This build is for maximizing mobility, Mesmer Skin charges, enough duration to secure a kill on a stunned enemy, and enough efficiency to recast Mesmer Skin with a single energy orb. You will need to bring a weapon that can kill Index enemies, especially for solo/public.

As the mule, you can assume you will never have an energy reserve. Whenever your Mesmer charges get below 10 (and definitely try not to go lower than 5), start paying careful attention and looking for an opportunity to grab an energy orb and recast. Some guides recommend [Rolling Guard] and using the invincibility to recast, but it's really not necessary to waste a mod slot on that. Just find a safe spot or bullet jump straight up and recast and you should be fine. Especially in Index, there aren't generally bullets and explosions flying around everywhere.

Mesmer Skin is the only ability you'll be using in Index. Note that 334 power strength (284 + 50 from [Energy Conversion], which you'll always have when you recast your 2) is exactly what you need for 20 Mesmer charges. Swapping [Intensify] for [Umbral Intensify] will not cross the threshold for the next charge so it's pointless here. You can squeeze 1 or 2 more charges out of it if you really try, but you'd have to [Sacrifice] something else important and it's just not worth it.

The mobility mods can be adjusted to taste, whether you prefer bullet jumping or sprinting.

And of course [Enemy Radar] is a must for Index. Being able to easily locate enemies speeds up the game immensely. With no companions in the Index, your aura is the best place left to get it.

As for Arcanes, I haven't thought about them too much for this build. I haven't delved much into that side of the game to be honest. I'm open to recommendations. I'd say focus on mobility or kill power. [Revenant] doesn't need help with defense. Don't take anything that triggers on damage because you won't be taking any.