More than 7 speeds on a freewheel? Ok for someone that rides moderately?

I am contemplating going from my 7 speed freewheel to an 8 speed because I want to go from a 14-28 7 speed to a MegaRange 14-34. Problem is my RD will not handle the 34 so if I have to buy a new one anyway, why not upgrade to an 8 speed freewheel? What I would ideally like to do is lessen the leap of 10 teeth as is on the 7 speed MegaRange which goes from 24 to 34 teeth. With an 8 speed freewheel, perhaps they would drop a 28 in there between the 24 and 34. Also I wonder what would happen if I just kept my “old” 7 speed freewheel (28,24,22,20,18,16,14) and somehow attached a 34T to it as an 8th gear (with proper spacing) if that would work. It would be good to keep that 28 cog so there would not be a jump in adjacent cogs more than 6 teeth. Also I have seen 13-34 8 speed freewheels and 11-34.

So my question is if I don’t ride hard, is it ok to use an 8 speed freewheel? My dropouts are spaced at 135mm from the factory. Also it would free up my old 7 speed freewheel which I can try to move over to my brothers bike which is made from spare parts anyway and has a 5 speed freewheel but he only uses the smallest cog as a 1 speed cruiser. I’d like to give him my old RD, chain (cut to proper length), 7 speed shifter… so he has some gears to play with. The front gear I gave him is the granny chainring from a triple I stripped down. I don’t know how many teeth but I would estimate between 24 and 28.