Well I think if you want a Sako TRG-22 for a tactical rifle you cant go wrong they are pretty good the fire control system on them is unique and its what i liked the most about them its designed so that you can do everything without having to taking your hand off the grip the safety is directly in front of the trigger and there is a leaver in front of the trigger guard to remove mag kinda AKish if little bit hard to use how its intended.
Down side of them is they are expensive and heavy it sucks to lug one around especially the bigger 42 Sako aftermarket parts are really expensive to the bipod and extra mag the bipod can be replaced to a regular bipod tho.
as for building a tactical rifle off the A7 or the T3 i do not recommend them they are over priced economy rifles i do not see them as true Sakos but as a example of Beretta marketing to produce cheap rifles for the first time gun buyer or casual hunter.
Manners might make stocks for them now but my biggest problem with them overall is the anemic recoil lug and over use of plastics.
The 85 series would probably make a good Tactical build the newer actions I cant remember what they were calling them have a set trigger on them that is superb and even when its not set its really good to.
But the problem with them is for your use is removing mags is a strange procedure you kinda have to pull the little tab back and lift up on the mag for it to come out i assume you want this rifle for practical rifle comp and that is not something you want to have to do when the clocks ticking.
Not sure if you can buy a bare action from Sako either in which case you would have to buy a whole rifle that cost around 1k at that price you might as well just buy a custom rifle
I am not sure there is much in the way of aftermarket parts out there for them either to turn it in to a real tactical rifle things like stocks extended mags.
Some people were saying Howa I cant comment on them I have never seen a custom built off one I hear good things about them from people who use them stock for hunting not that matters much tho.
CDNN had Fn spr actions for a good price around $400 dont know if they have them anymore I bought one a while ago for a build its not the best thing out there stock but you can make it pretty good its a solid action to build off of but you can only buy them in SA and 308 and 300 WSM
That leaves you with a host of custom actions.
Perhaps look into BAT or Nesika tactical actions the latter is one sexy action people know what it is when they see it but its pricey.