Reddit mentions of 1/72 Scale Macross ADR-04-Mk.X Destroid Defender Construction Kit

Does he like Mechwarrior, Mechs, and giant stompy robots in general, or is MWO his introduction to this particular IP?

If [a] you would like to give a tangible gift (eg not digital goods, not a gift card for digital gifts) and [b] you think he likes Mechs themselves (as opposed to just liking the video game), then you can buy mech models.

For models, you have three broad choices. (1) You can buy Mech-branded models, (2) you can buy non-Mech branded models from Japan that nevertheless look a lot like Mechs because of copying, or (3) you can buy completely unrelated models that are nevertheless giant stompy robots (if you know he likes giant stompy robots in general and not Mechs specifically).

(1) You can buy the Mechwarrior or Battletech-branded models, which are smaller, cheaper, and usually come pre-built. If you search "Mechwarrior" on Amazon.com's "Toys and Games" category you will find pre-painted plastic models. If you search "Battletech" on Amazon you will find unpainted pewter models that he will need to paint himself (which he probably isn't into if he just likes the computer game). You can also go on ebay and search "Painted Battletech ____" filling in the blank with the names of mechs you know he likes or are in the game to find pre-painted pewter Battletech models. (You can go to mwomercs.com and look at the art gallery for the names of mechs that are in the game.) Note that sometimes the pewter models don't closely resemble the mechs as they appear in-game, though.

On the plus side, these are branded appropriately and quite cheap. However, these models are intended to be used in board games, so they're smaller less physically attractive as pure display objects, and IMO just don't look very good.

(2) For more attractive models, you might want to look at model kits from Japan. Now, there are no Mechwarrior-branded models from Japan, BUT some of the iconic mechs were actually copied from Japanese anime IPs of which there are model kits.

This is the Japanese version of the Rifleman mech, and has the added advantage of closely resembling the Jagermech (which is actually in-game)

This is the Japanese version of the Warhammer mech, but has the disadvantage of not closely resembling any mechs that are currently in the MWO game. Nevertheless, it's something he would appreciate if he's into Mechwarrior in general and not MWo specifically.

The larger the model, the more expensive. 1/60 scale is larger than 1/72 scale. I would be wary of buying random anime robots as the aesthetics are subtly distinct and your BF might not like the anime style as much. But if you stick to the anime robots that were copied for Mechwarrior, then it's much safer.

The advantage here is that the models are quite large and attractive. The disadvantage is none of the models will be Mechwarrior-branded and there are no model versions of the Mechs that are currently in-game, only other Mechs in the universe.

(3) Finally, for someone who just likes giant stompy robots in general, you could get him some Pacific Rim models, which are quite high-quality in build and look pretty great. This, for example. Obviously if he loves Pacific Rim this would be a much more appropriate gift.