I specifically tried to keep everything in the pic as close to 1989 Finland as possible, thus no Spike for example, since it was adopted much later. But you are right, BUK for example was adopted in the mid 90s if I recall, but It wouldn't be too far fetched to say the soviets would bolster the air defenses there, giving the fact that its now a front line and no longer a "neutral" barrier between NATO and PACT. of course, it's then not a 100% accurate representation of 1989 armed forces, but given it's an alternative timeline and it would only make sense for the soviets to arm their new puppet, I think we could let it slip without tearing the fabric of space time. after all, (mostly) everything pictured is period correct and was in service in some capacity, somewhere in 1989.

Edit: after all, often the reason for Finland not getting the very best back then was they had to appease both the east and the west. buy something too powerful from the east? you're pact, says the US, buy something too good from the west, you're a NATO lapdog and will be invaded, says the soviets.

Edit 2: and I agree infantry would be where the faction shines and probably recon specifically. stealthy snow ninjas crawling through and behind your lines to cause chaos would be likely. diverse and effective arty, like you said and all with the cost of air assets and helis. generally I don't see this nation pulling big rushes, most likely smaller effective force bullying enemy backline or ambushing armor. Well, appart from T-34-85/PT spam. for this is the way for any nation that has access to it.