reviving my T420, considering upgrades

I'm considering ditching my 2015 macbook pro and looking into upgrading some parts of my aging T420. The specs are in the link with screenshots.

http://imgur.com/a/GMcLN

1. The original 6-cell battery is dead. Alternative options: http://www.ebay.ca/itm/9-cell-Batte...3f843ae&pid=100005&rk=3&rkt=6&sd=130964831843
   
   
2. I really don't use a DVD drive. I used to have an HDD caddy. But I already have an mSATA. So the original hdd caddy can be populated with either a 1Tb HDD or 500gb SSD (not in a hurry at the moment).
   
   
3. Will need a new keyboard as it won't turn on by pressing the power button for some reason. No green light. No orange light when I mute speaker/mic.
   
   
4. Wondering if I can upgrade the CPU. Worth it? I know more powerful cpu = more battery. But if I'll get normal 6cell and ultraby 3cell, I should be fine, right?
   
   
5. I'm ok with my current 1600x900 TN panel. Not thinking of upgrading any time soon.
   

I would like your suggestions please.

 

I believe it's doable, but the only ones that might be worth it are the quad cores. Unfortunately, the 35w quad cores didn't come until the T430, so heat was an issue on the T420 with 45w quad cores.

 

I'm thinking of selling my T420 and getting a T430.
Or maybe save up a bit more and aim for a T450?

 

Just my own personal opinion here, but I think the T450s is the best of the recent 14" ThinkPads. You get a factory IPS option, and the ability to do a SSD and hard drive. I'd probably have one, but can't come up with a compelling reason reason to get rid of my Dell, which is decent and still under warranty, but I don't use my notebook enough to justify spending a couple hundred to upgrade. Last year, they had some T450s in the Outlet sub $500. I should have gotten one, but you snooze, you lose.

 

T450s, not the regular T450? I thought the slimmer version weren't user upgradable?

UPDATE: scratch that, I've been reading about it it looks very intriguing. Found a refurbished one for $550 CAD. Might consider!