The problem is, even with just the default ~50 add-ons installed, You're going to have a minimum of atleast 5 controls per add-on (name, enable/disable, update, report bug, delete) which already adds up to 250 gui controls being created and rendered all at once. I think we use about 12 per add-on in v3 which is about as minimal as it gets.
Staggered gui building will be the best chance, doing 50 controls, sleeping for 10ms then doing another 50. That will prevent the game slowing down and only add a tiny waiting time for the Your Mods section to load.
On the topic of stats, I looked into methods of counting bricks planted etc. reliably but it involves putting a lot of trust in server hosters. Originally in RTB 1.05 I had a profiles system that counted a bunch of "useful" stuff like times you'd been kicked, banned, how many bricks you'd placed and movements you'd made. But all of this was supplied by the server and considering how many idiots we have running around hosting servers I think this would just get abused and the stats would be nowhere near accurate. I like the idea of server visiting though, it might be quite an interesting stat and could be aggregated into data that could be used for server rankings. I'll look into that one for sure.
RTB does track playtimes at the moment though, here are the top 10 RTB users by hours of usage:
I have not (6138) 1221 hours, 08 minutes
Disconnected (8530) 1050 hours, 12 minutes
Jakob (14941) 1030 hours, 60 minutes
Cucumberdude (4708) 1017 hours, 22 minutes
Darkness Ninja (12899) 966 hours, 02 minutes
Benofdoom (1436) 920 hours, 02 minutes
Furling (6796) 915 hours, 50 minutes
Dandodeys (3050) 857 hours, 07 minutes
paulguy (3825) 830 hours, 18 minutes
clone (4326) 820 hours, 51 minutes