I had Seven swap a 1 inch headtube for a 1, 1/18 about 10 years ago on an Axiom that I no longer own. They did a fantastic job, and you wouldn't know it had ever been done.
So, in terms of 'can it be done'? Yes. In terms of 'are they good at it'? Yes.
Now the more tricky question 'will it make a difference'? Honestly not.
I had my 1 inch swapped because it was getting hard to buy forks. In terms of the performance advantage of a 44mm head tube and BB30 bottom bracket vs 1, 1/8 and standard English threaded, I can comment from experience.
I own a Seven Axiom SLX with standard English threaded bb and 1, 1/8 head tube. I have a Colnago Master with Italian threaded bb and a 1 inch head tube. I also have a Moots RSL with a press fit BB30 bb and a 44mm headtube.
Let's take the bb first:
Honestly, other than the aesthetics of the Moots looking more modern, the oversized BB doesn't make a difference. It doesn't feel noticeably stiffer because I run the identical Super Record chainsets on all 3 bikes. So, the axles and bb bearings are identical in all 3 bikes. Comparing it to the Colnago is difficult because it has a super stiff cast bb shell. So, actually this isn't quite 'apples with apples' as despite the smaller diameter of the tubes butting up against the bb, and the inherent nature of steel vs ti, the Colnago is still stiffer than the Moots. I had the Seven built stiff, and as you know, Seven can make ti feel as stiff or compliant as you want. Nevertheless, I can feel only a tiny (and possibly only psychological) difference in bb and drive stiffness between the 2. Blindfolded, I couldn't tell the difference.
In terms of press fit BB30, I have not experienced any problem with the Campagnolo press fit BB30 UT cups, unlike some people. I used plenty of molybed grease during installation, and it has been quiet and movement free.
The advantage of the larger bb is often to allow a bigger down tube and stays to attach to it in order to increase stiffness. Now, first question is do you subscribe to the 'stiffer is better' philosophy? There's a whole other discussion right there, but if you do, ti probably wasn't the right choice in the first place. Let's assume you were drawn to ti because of its comfort. Since having a new bb retro-fitted won't enable Seven to install bigger stays or down tube, you won't get most of the benefits anyway.
Since you want to fit an SRM which I am guessing is BB30, then this would be the only reason to swap.
Now the headtube:
Is tapered 44mm stiffer than 1, 1/8 or even 1 inch? Again, not noticeably. Given the length of most headtubes, you won't notice much of a difference in the frame itself. Much like the intersection of a BB30 and the downtube, a 44mm headtube allows for a larger (and therefore stiffer) interface with your forks. But again, is stiffer always better? And is a 1.5 inch fork crown really that much stiffer than a well made 1, 1/8 fork crown anyway?
Much like my decision to replace 1 inch with 1, 1/8 all those years ago, it has a lot to do with future proofing your bike. Non tapered forks will become increasingly difficult to get hold of at some point, and the handmade, metal bike market does seem to be transitioning towards a 44mm standard to allow for either tapered or internal headsets and forks.
So ultimately, Seven will do a great job for you. In order of priority, I would probably change the headtube (but be aware of the geometry changes necessitated by either a tapered external headset cup, or a non-tapered internal headset cup), but I probably wouldn't bother with the bb. On a new build, yes because it can facilitate a larger downtube and stays. As a retro-fit, the risk of creaking and problems with adapters probably makes it better to save your money and invest in a better chainset and bb instead.
Hope that helps!