Hello. I've addressed this with the fact that you are wanting MODERATE VELOCITY 150 GRAIN BULLET performane from the 7mm RM.
So on those terms I cannot see ANY benefit (unless you are getting a quality rifle dirt cheap) that using 150 grain bullets in a 7mm RM will give you and many disbenefits. You already have a .270WCF and whilst I would not advise you to go down the .280 Remington (as it is too obscure here in UK) route here's my 2 pence's worth:
1) You can already get decent, good, 150 grain bullet loadings in the .270 as factory ammunition. These will give you what you want to achieve with your 7mm RM but additionally you will have one extra round capacity in the rifle and no feeding issues through the useless and unnecessary belt on the 7mm RM. I tried some years ago a P-Hale 7mm RM. It fed the first round from the magazine well enough and the second with reluctance. It jammed on the third round. Every time.
2) If you handload you will be using more powder in your 7mm RM to get exactly the same velocity that your .270 will give for less powder. And no issues of maybe, or maybe not, needing to use magnum rated primers.
3) It will be a bitch to sell here in the UK. On the plus side used 7mm RM dies from the USA bought off eBay will be cheap.
Now, if you are talking using 160 grain or 170 grain bullets that all that changes. Except of course that RWS now does 155 grain Evolution loads and SAKO did do the 156 grain Hammerhead (and component bullets too) in .270. And your template calls for merely 150 grain bullet loadings.
So it is only if you are going to heavier weight bullets that the 7mm RM offers any advantage and that, only, because it takes .284" diameter bullets.
So in conclusion:
a) Stick with your .270 and just buy or load 150 grain bullets.
b) Whilst .280 Remington does it well enough, better than the .270 IMHO, it is too obscure here in the UK.
c) The 7x64 is brilliant and you'll get all that factory TIG, TUG, H-Mantel and other German "exotics" as factory standard.
d) If you do want another calibre other than .270 the bog standard ordinary 30-06 will do it all, without fanfare, with the least bother and at the least cost with 150 grain bullets at moderate velocity.
I've a .270 and a .280 and have just put in for a variation for a 7x64. But the feeding issue and the loss of a round capacity puts me off the 7mm RM. And the waste of powder...
Here in UK?
If you want a 7mm RM on the basis of wanting a rifle to fire moderate velocity 150 grain bullet loads? Get a .30-06...it will do ALL that and go up to 180 and 200 grain bullets too at moderate velocity.