No it really isn't. Here's a list of Ostheer units that won't be affected:
Literally all of them except the mg42
"Oh but it will effect timing and it delays other units"
Very VERY slightly yes. If you think this will be a critically debilitating change than you have an unhealthy bias towards Ostheer.
Then of course there's the fact I've already said I want to increase the cost of all MGs. And the performance of most of them too
You are forgetting the time frame factor. The nerf you are suggesting is in the first ostheer unit and even small nerf can have a huge impact, this has been clearly demonstrated by the changes in Reckon commander and the huge impact changes in timing turned an average commander into an OP commander.
Ostheer have the best HMG (and they already have lost their superiority in their other support weapons) by design and there is hardly any reason to nerf it unless one want to change that design.