MWO is not produced by the same people who made previous MW titles. They can not use anything from a previous titles, besides what the BT franchise can/will let them. This means that mechanics from older games can't just be dropped into this one. (Such as the old mechlab, weapon styles, etc.)
The developers of this game wanted it to be more based on lore than previous MW titles where. Lore is mostly the table top game and the novels. So, a lot of the systems being used in this game have been based on the TT (Table Top) system for Battletech. This helps to differentiate this title from previous MW titles, as well as brings back a sense of the older battletech some of us still recall and love.
There has been some minor talk from PGI about having computer driven vehicles within the game, as well as a single player mode. However, these plans are "not for a very long time to come" before they really becomes considered. Read above about previous MW titles and MWO.
MWO may be based on Cryengine, but PGI had to just about rewrite the coding for Cryengine to make mech combat work. Cryengine was not designed for multiple weapons fire, units having "health", and a single unit having "different sections of health". It also has caused a lot of problems for missile based weapons in the past, as most of the missile coding is apparently written by PGI and not well supported by Cryengine.
Due to the extra load on Cryengine with having each mech have different sections, as well as having some weapons that can throw out up to 20 individual missiles to track in the game (for a single weapon, forget the rest), the servers can not support (till they streamline things more again maybe) more than 24 players in a match. (They probably could to more. So, why 24 players? Read up about lance and company formations on Sarna. We are basically fighting what would be considered probably a standard mech engagement for the BT universe, of a company of mechs vs another company of mechs. Each company is broken down into lances. Each lance is broken down into four mechs. Thus why it's 24 mechs total, 12 v 12.)
There is no relation that I know of to PS3 or Xbox for MWO. Those where different titles you probably experienced. (Example: Mechassault was on the Xbox, produced by Microsoft. Had nothing to do with PGI at that time.)
Respawn is not in the game as, in BT lore, once your mech is down, you are out of the fight. No magic repair. Not to mention, no respawn also is suppose to force players to play more tactically. This game was described as a simulator of the Battletech Mech combat.
Repair and Reammo (R&R) was removed due to some problems with income balancing, as well as some abuse. The abuse was the fact that you would get some ammo back for free, and then have to pay for the rest. Most people just didn't restock their ammo and took the free ammo instead, which was not the intent. So people where going into matches with less ammo than max. You also had people who would not repair their mechs when they were grinding c-bills. This lead to half dead mechs (as you would get free repairs enough to get the mech mobile again) on teams. These half dead mechs from the start of matches often would die extremely quickly and not contribute to the match, basically griefing the team they were on. There were other factors as well in it's removal.
Right now, we are looking forward to Community Warfare (CW). CW is suppose to let factions (or merc groups) fight over planets inside the Inner Sphere (lore based). Based on each factions performance/your contribution to the cause, your faction and you will gain extra benefits. Beyond that, expect more maps and mechs to play around with. (We are also looking forward to the "clan invasion" which will introduce a new mech type, omni mechs, into the game. If you want the dual AC20 on your mech, go to
Sarna and look up the Direwolf (Dashi). For what clan mechs you can eventually get, look at the clan package being sold.)
We are suppose to see destructible terrain at some point. However, there are concerns about the lag it can cause to the system with an MMO such as this one. PGI is still trying to figure that one out.
Probably coding and datacalls. Those games might have had less data calls than MWO does. Recall that MWO, you have several health pools, a health pool for each section of your mech. And, each section of your mech can be targeted and shot at. You also have to consider the accuracy of this game, compared to the accuracy mechanics of a game such as WOW.
The game you are thinking for the Xbox was called Mechassault. I own it, but my Xbox360 could only play one of the two games, and then my 360 died... so I have as of yet to really play that game beyond a little test run.
I don't think you would want to try and play a continual live action style of MWO. You'd be technically waiting weeks or even months to get from one place to the next or for mech repairs... Beyond that, to have the system you are kinda hinting at, CW and the new Launch Module will provide some similar concepts.
MW3 was a decent game. This game has better Graphics. Game play, they are each different enough to make them too hard to compare for me. If you had to ask me, I'd say I like this game a little better, as I find game play smoother and the combat system more fluid.