If you haven't already, you should consider a backup compression tool, like LiteSpeed, to reduce the size and run time of the log backups and regular backup.

If you aren't doing it already, and it is possible with your table structure, consider table partitioning so that you only have to reindex the active partitions of the large tables.

Consider reindexing some indexes one week and others the next week, especially for very large ones. There will probably not be much query performance impact from letting it go an extra week.

Finally, if the only problem is that the log backups take a long time to complete, that isn't really a problem as long as you have enough space in your transaction log file.