Ugh, as others will no doubt jump in to tell you, you could get away with 32 MB RAM for basic router operation, and maybe some really lightweight additions if you really know what you are doing.
But those 16 MB RAM are basically done and going home to cry directly after booting, running OpenWrt on 16 -- let alone 8 -- MB RAM is virtually impossible.
Buy the chip, if you ever find it, and license their Linux-based SDK, because you're going to need more than luck on that.
@rosysong I'm currently also replacing TSSOP 32 MB RAM chips with 64 MB. It's no fun and inhaling the flux fumes is not healthy. We've already thought about collecting the routers and sending them to Africa either as a donation or for upgrading. Salaries are high in Europe. It's not a economic decision to reuse the routers, but an ecological one. I dislike that TP-LInk saved at the wrong end (but I love them for donating 2000 routers to us 
). If you have any influence on the choice of the RAM/Flash chips, tell them 16 MiB flash and 128 MiB is the minimum a future proof router should have. These are not parts on which one should try to save money. Everything else is electronic waste. We'll likely dispose 20,000 of those 4/32 MiB devices in the next 2 years. 8-16 MiB RAM are by far not enough. Even the crappy VxWorks routers need 16 MiB RAM. For proper WLAN/Ethernet performance you need at least dedicated 16 MiB for queues. 32 MiB are not able to hold the whole decompressed SquashFS thus you have a performance penalty when inodes need to be read from flash and be decompressed again and again. 64 MiB RAM gives proper performance with a single ath9k WLAN device, but if you have a second chip or just a single ath10k device, you need 128 MiB. 64 MiB ath10k devices crash very often due to OOM.