It might be worth mentioning, that around when I started playing hawken; within a week from the date 3/3/13 I was placed into a match with a player who still posts here and has been among the very top players in hawken (I'm not giving a rank number because last time somebody got on my ass for not giving an up-to-date player ranking even though the person mentioned held that rank at one point or another. Jaysus).
This was a long time ago, yes. That player was like a god of hawken to me. Aside from completely dominating the battlefield my only other interaction with that player was him practically shrieking at me through Voip to not go into the turret mode of my new test drive grenadier and that I'm an idiot. These things burned this player's callsign into my mind.
Back then I had no knowledge of what matchmaking was or that anything was even done to place players in matches according to their skill range. I rarely ever ran into the same player ever again after leaving a match because there were so many more people playing then. I have absolutely no idea what numbers we're talking about but there were a lot of players.
I don't know if and how matchmaking has been changed aside from basic scaling of the window where players can join a match since that faithful day, but assuming it's not too significant I'm confident that no matter how many people are brought into this game, there will always be a chance for a significantly stronger player to be placed in a game with you.
There will always be a chance for stomping, regardless if a person's mmr correctly reflects their skill, or if it's a returning player working their way back up to where they sat before they stopped playing. I will also say as far as an old player working their way back up, mmr is far more retroactive than many people assume. If you're doing significantly worse, or significantly better, that fuzzy bunny shoots up or down fast. I fluctuate so damn much I see this so often. Drops and spikes of as much as 11 mmr per match.
The devs have noted our concerns, and have made it vocal that this particular topic also concerns some of them as well. As far as I can see, no real issue has presented itself yet to the grandfathering of weapons. Trying to fix something that has yet to present itself as a serious problem may inadvertently cause more problems in the future. Let's see how this all works out, and then combat anything that becomes concerning about this topic. There is always the option for re-balancing, labeling, and restricting these old mech loadouts if and when it becomes needed. I would personally rather the development team focus on making sure everything DOES transfer over, and making sure that the PC build remains fairly playable after the upcoming patches than trying to fix something that is as of right now far from broken.