I feel like it wouldn't be right. If they did remake some of them with Matt. Somehow the whole series would be out of sync. But that's just my opinion.
To be honest it is a bit of an ill formed idea of mine based on discussions I had in the pub with friends. I am not entirely sure how I would feel either. I suppose it feeds into the canon discussion as well - this would seriously screw with canon (and for that reason alone I find myself warming to the idea).
I also wonder how it would work if some form of CGI magicfulness was used (in a Trouble with Tribbles stylee) to utilise episodes of lost stories. Like I say, I am not convinced myself - but it was partly the success of the Big Finish production of Shada and partly watching Never Say Never Again which got me thinking if there was any way to revive the work of the brilliant writers whose stories are seemingly lost forever.
I see where your coming from and yeah new effects would be good in the old series. Renewing them and whatnot, giving them a facelift. It would be interesting how they would go about that. If they wanted to do something like that.