Seems to me that you are feeding 2 types of chaff (Alfa Oil and low molasses chaff) and 2 sources of oil (Alfa Oil again and linseed oil.) You’ve already got 3 definite sources of fibre in there (2 chaffs and Speedibeet.) I don’t know what horse and pony mix you are using, but if it is a proprietary complete feed it could have all of the vitamins and minerals in it already (you need to check the bag) so you might be doubling up on those too with the topspec. It seems to me that you are feeding quite a lot already without needing to put more linseed in there as well. Having said that, linseed is great stuff and goes a long way for the price.
For me, you need to know why you are feeding each thing, and make sure you are feeding appropriate quantities.
Fibre should be the basis for your feed, and speedibeet is a good source of non-heating fibre and is good for getting fluids into reluctant drinkers when there is little other moisture in their food. Both the Alfa and chaff are also good sources of fibre, but the Alfa will also have a higher energy value.
You need vitamins and minerals. These can come in a balancer, or in a feed mix or cubes, or in a powder supplement. (Top spec will be unlikely to tell you, but they do a V&M powder in bulk which has the same ingredients as the balancer but without the whatever it is that makes it little pellets. It is much more economical to use.)
After that, you would be feeding for a specific nutritional need. Eg doing a lot of work? Need higher energy content. Poor condition? Need something to build horse up. Etc. But know why you need to feed more.
My horses, in a range of work from very light hacking 2-4 times a week up to endurance-type fitness regime for competition all have their basic feed based around speedibeet, vitamin supplement and chaff. 2 of them also get micronised linseed (one for his joints and condition, one for his coat.) The competition horses are getting horse and pony cubes for a bit more energy, I will build these up as they do more work depending on need for energy and condition. I give all my horses salt. Each horse has supplements according to their individual needs (one needs all manner of joint and respiratory stuff atm, he is getting old. The young competition horse does not need anything extra.)
On the whole, you shouldn’t need to be putting lots of different things in your horse’s feed bowl though. Especially if you aren’t doing the work for it.
A last note - you are feeding your pony top spec balancer ‘for the topline…..’ there is no feed that will give a horse or pony topline. Topline is the muscle built up over their back and neck through correct work. If they are doing the correct work, they will need sufficient correct nutrients to help them build muscle. This varies from one horse to another - some will build muscle on forage alone, others will need more feed. All horses and ponies need vitamins and minerals. Wild horses would browse many kinds of plants which would give them access to a range of nutrients, but we limit our tame horses to one field of grass and some hay, which narrows their nutritional range, so we need to supplement their vitamins, in the form of balancer. Balancer will not build muscle. For a Welsh A you need to be careful you do not overfeed, as their necks are often the first place they will show an accumulation of fat (a crest) which can be mistaken for topline.
A balancer and low cal chaff is probably all he needs, but again - as I said above - know WHY you are feeding something.